Denon 3802 or Onkyo 898 w/QSC USA900 for 2 channel

Someone on this site gave me the idea to use a decent Home Theater Receiver and pre-out to a decent amp for 2-channel stereo. Is this wise? Is there a discernable difference between Onkyo and Denon? I want the latest technologies, Pro Logic II, DD EX (only matrix in Denon), DTS ES etc. Will these operate well enough as pre-amps? Also, is my 4 yr. old QSC USA900 pro amp a decent home audio amp? It's rated @ 240 watts/channel @ 8 ohms.
The latest technologies don't do you a whole lot of good if you are running two channel. Both the Denon and Onkyo are decent recivers, but in the same price range, I'd go for a Rotel RSX-972, maybe the Outlaw reciever or a Carver C-1000. I personally think both the Denon and Onkyo units you are looking at are a tad overrated, but I may be wrong. The build quality of the Rotel and Outlaw units are far better than the Denon or Onkyo, the Carver I don't have any personal knowledge of, but I've heard good things about it.

The QSC USA900 is not really a (for lack of a better term) "home audio nut" amp, it's ment more for DJ, stadium or club use, and as such, it does a good job. For serious home audio or HT use, it has way to much distortion. Here are the specs on the QSC USA-900 amp (your info of 240 was a tad off)..

Output Power (per channel):
Continuous Average Output Power Both Channels Driven:
8 ohms, 1kHz, 1% THD (typical): 125 watts
4 ohms, 1kHz, 1% THD (typical): 200 watts
2 ohms, 1kHz, 1% THD (typical): 250 watts

My thoughts anyway, I've been known to be wrong!
I recently tried the same thing, only using a Harman Kardon AVR510. It was a huge mistake. As much as I wanted to consolidate my home theater and two channel into one system, I was wholly dissatisfied with the sound. I decided to buy a tube preamp and run the CD into one input, and the pre-outs from the HK into the other. This way, I can easily switch out the HK from my two channel system entirely. To my ears, the HK, which sounds just great for home theater, sounded bright and edgy for two channel playback. If I were you, I would just pick the receiver you like the best for home theater, and as long as it has pre-outs, just get yourself a nice used preamp to switch back and forth like me. Just my two cents.