I just ordered the Emotiva Ultra Theater LMC-1, LPA-1 today and I'm about to take the plunge on a 5.1 or 7.1 Axiom's.
I'm holding off on the order until the sample of the finish arrives and until I can sort out if I want to add the back two surround speakers.
My room is 14' wide and 20' deep and I've choose M60's, VP150, and QS8's for the surrounds. I currently have two Velodyne 10" subs and I do have the placement available for all the 7.1 system.
Now I know that the material to take advantage of the 7.1 really isn't out yet, but... Have those who have added the 7.1 back two speakers really found that they were worth it?
Also I do plan on adding a HD disc player in the future.

I'd love to order that Emotiva for $899, it seems like a great deal but unfortunately by the time I ship to Canada between the weight and duty I'd be paying double the cost. But it looks like an awsome system.

Your correct, but technolgies like Dolby PLIIx will take 2-channel and 5.1 movies and make use of the rear speakers for a full 7.1 experience.

Every movie I watch is done in either "DD + PLIIx" or "DTS + PLIIx" modes, most receivers will achiever this if it has PLIIx.

By the way, I LOVE my Emotiva MPS-1 amp.

7, welcome. As Randy points out, the material to take advantage of a 7.1 setup has been out for many years, even if there was no such thing as a discrete 7.1 channel format. DPLII and other similar processing extracts the natural ambience present in 2-channel source materials(in varying degree)and steers it to 2-4 surround speakers, where it belongs. DPLIIx leaves the front channels unaffected, but operates on the side surround channels in 5.1 material to extract surround info which should be imaged in back and sends it to the back surround speakers in a 7.1 setup.

Just this week I removed the extra rears and went back to 5.1 I didn't find enough difference at all to make it worth while.

Now this part could be me, but I found that suround effects were actually more pronounced when I disabled the rears and went back to straight Dolby 5.1 or DTS processing instead of PLII to 'trick it out' into 7.1

Could have all been in my head but I guess it is possible that since my rears were not nearly the quality of speakers that the rest were, I was missing out a bit on whatever PLII decided to send to the rears instead of the surrounds.

Regardless of the technical truths, it was already a perceived truth in my head and therefore the easiest thing to do to make me happy was to remove them.

Ahh, another Axiom/Emotiva club member. Congrats on the 'ultralight' combo! You'll love the LPA

I'll be curious to hear what you think of your system once it's all up and running. That LMC would be such a nice match to my LPA.

As to your question....

I once had a 7.1 setup in my den and was somewhat unimpressed. Even on DVD's with DTS-ES or DDEX, I never really felt the extra channel(s) did much to enhance the experience. IMHO, a properly setup 5.1 system will deliver 99% of the experience of a 7.1 system.

Murph, I assume that you meant DPLIIx, since DPLII doesn't work on multi-channel material. If so, the general view is that having speakers in back to image sounds which are intended to come from behind is an advantage.

Since DPLIIx does in fact extract material from the side surrounds in 5.1 material(which is about equal in level in both surrounds and is supposed to represent sounds from the back), they don't play that material, and if the back surrounds are far poorer, as you suggest, the result of using them might be disappointing.