Can anyone explain the differences in these models?
I have two Sound and Vision Buyer's Guides (2003 and 2004) and there doesn't seem to be much different in the models, other than:
AVR 430 7x65W
AVR 525 7x70W
AVR 630 7x75W
The AVR525 didn't have Dolby Pro, whereas the others do.

Is the older AVR-525 missing any new options, or are new models brought out just to increase sales?

Nope, the 525 does have Dolby Pro Logic II. It's the sound format I use most often... On quick glance, I don't see much difference.

The 525 is a great buy. You can get a reburd from HK's ebay listings for $500 shipped. Yes, HK posts on ebay, and it comes with the full warranty. They post under harmanaudio.

I think the 430 and 630 have Dolby Headphone, and quadruple bass management. The 525 that I have, has triple bass management.

I think the bass management that HK offers is a good thing for Axiom owners since the -3db points of the QS surrounds and VP centers are much higher than the main speakers.

if i remember correctly the 630 has slightly more rated power-5 watts per channel-but not much else. if you are going to go the HK route, i suggest getting one on ebay for 500(mine was 470 and shipping 300. but, if i could do it over again, i think i might of chosen a yamaha 1400. with onboard EQ feature and upconversion it may be worth the extra 250 dollars

What is the difference in Dolby Pro Logic and Dolby Pro Logic II. Sound and Vision lists HK AVR-525 as only having the DPL II.

What is upconversion...I thought I saw it mentioned on another post, only one cable required for video games, etc (Whereas the HK AVR-525 would require separate cables)? I won't be using video games, so will that make a difference.
Alan Loft recommended HK, Denon or new NAD for their robust power supplies.
I also read where most receivers had a sound tone sent out for setting up the system (Know little on the subject...maybe someone could elaborate).

imagine you have your dvd player, VCR, camcorder, and computer hooked up to your reciever. you would need a separate audio and video cables for each component. without upconversion, you would need a separate video cable for each component to plug in to your tv. So, you would need 3 video cables from components to your reciever, and 3 video cables from your reciever to your tv. this is a problem if you dont have enough cables, and if you dont have enough input jacks on your tv.
with upconversion, you only need one cable from your reciever to TV for S video, component, and composite. S video, component and composite are the different types of connectors and wires used on TVs. do you know what those are?

most recievers have a basic test tone to set up your system. the HK's use a pink noise test tone. this is only used to calibrate SPL levels. SPL is basically the volume of a certain sound. by using a pink test tone, it covers the whole frequency range and can be done very easily. the object of SPL calibration is to make sure each speaker in a 5.1 setup is giving equal output. The HK's test tones don't work with a subwoofer though. In most cases you will need to buy a dvd/cd calibration disc. A calibration disc will cover the whole frequency range is more helpful in setting it up.

i think the difference between DPI and DP II is that DP II is better. i think DP II can do everything DP I can do, but it is the later version. i am not exactly sure.

any more questions?

More questions.
I don't know the difference between composite and component.
I now use, what I would call a coaxial cable between the tv and Direct Tv Receiver...then the same to Direct Tvs wall jack (Direct Tv has satellite Tv provided to the entire apartment complex).
I assume this is either the component or composite type.
I have seen the larger circular "S-video" hookup, which I have heard is clearer (but my tv signal arrives on coaxial cable, so a ft or two between the Direct TV receiver and Tv shouldn't make too much difference.)
Reducing the connections between the receiver and Tv sounds like an important option...I don't think my Tv has additional input locations.
Does the Yamaha RX-V1400 set up the sub as well?
From what I have heard the Yamaha RX-V1400 should work fine on all but the M80's which have a lower ohm/higher current setup.

i will start from the bottom up
the m80s are axiom's most sensitive speaker which means they need the least amount of power to get loud. the 4 ohm load should work fine on the 1400. i have not read any threads about this being a problem. But, email axiom if you are really worried. they will give you the final word on that

what components will you be connecting your tv too? dvd and direct tv and what else?. what connectors are you using to connect this to the tv? also, how many inputs do you have on your tv?
S video is a better wire and connector. some say it increases picture quality by 40% over standard RCA cables. you wouldnt get S video because of a long cable run, you would get S video because its better then RCA. ( i have not seen S video myself though. my 90 dollar KLH tv has 2 rca inputs and thats it.)

Dolby Pro Logic II is an extension of Dolby Pro Logic. It is, in essence, a better translator of the DPL signal.

Hawkson is essentially correct about video upconversion, but I would point out that if all your devices are s-video (for example), you only need a single S-video connection between your receiver and TV. If you have different devices with different inputs, then you would need multiple connections.

Composite video is a video signal transmitted on a single RCA cable. S-video splits the signal out to 4 parts (I don't remember which) and transmits over a similarly sized cable, with different connetors. Component video uses 3 RCA cables/jacks (I believe it's similar to S-video in which signals are transmitted. Could be totally wrong).

Your coaxial cable is a different sort. That is an RF (radio frequency) signal that carries audio and video, and is therefore the lowest quality. You should be using composite or S-video between your DirecTV receivver and the TV, as the DTV receiver will translate the signal. (someone else want to step in here?)

A big question is what kind of TV you have. What inputs are available?

TV's a piece of trash.
I was originally thinking of buying a cheap receiver for music only...thinking the receiver would become outdated by the time I had a full fledge HT system.
Then I started looking at upgrading...If the receivers don't change too much in the future I might as well put the extra money in now, and I'll already have a receiver capable of expansionn, along with front speakers (probably m60's). The better TV, VP150, QS8's and sub could come sometime in the future.
I can't see HT expanding much beyond 5 speakers, maybe one or two in the back...but then who knows.
I just wanted to make sure on the receiver. I might just get the Denon 1804 for ~$350, and plan on replacing it when I get more serious...at least the speakers should be good for a few years.