I am brand new to home theater and was hoping to get some advice as you look like a very knowledgeable bunch. I have always been a big 2-channel music guy and I am now ready to enter into home theater. Here is my situation:

I bought my receiver used for 150 bucks off of eBay a few years ago and have been using it as a stereo only receiver with my DVD and satellite system. It was a near top of the line receiver for Sony ES...back in 1996. It has no digital inputs and I believe it only has the original Dolby pro logic surround decoding capabilities.

Recently my father put together a beautiful home theater with Pioneer Elite electronics and Paradigm Reference speakers. I was so impressed that I decided I would like to put together a system. I don't have the same funds as he does so I will need to build my system piece by piece. So I decided to take some nice spare speakers that were sitting in a box in the basement and use them as my surrounds and buy an Axiom center channel to get a basic system going.

Here is my system:

Axiom M60 main speakers
Axiom VP100 center speaker -brand new
ADS 310 rear speakers -just hooked up
Harman Kardon DVD50 dvd player
Sony ES GA8ES receiver
Threshold S350e amp -now powering the M60s

My receiver is 120 wpc across the front 3 channels and 50 wpc for the rear channels but it has a 'power swap' feature that will put the 120 wpc to the rear channels if you use an external amp so I decided to give it a try. I added the Threshold amp (my pride & joy and the by far the best piece of audio gear I've ever owned) from my upstairs music system to power the M60s and used the 'power swap' feature. Wow what a difference!! The depth of the bass, and the 'quickness' of the speakers improved tremendously. There also was better channel separation when listening in plain ol' stereo.

So now my question is what should my next purchase be? A sub or a new receiver? Would a sub add a more immediate and noticeable enjoyment or a receiver? I am guessing since my receiver is from the dark ages that would be the next logical step.

Any features that I should pay particular attention to? Brands/Models that I have to make sure to find out more about?

I watched the Lord of the Rings movies and really enjoyed the surround sound aspect. I am looking forward to watching more movies soon.

Thanks for any and all input.