Help and advice needed re: amp usage

Several years ago I jumped with both feet into HT. Ditched my two channel stuff and built a decent HT system. After all, they told me, the HT set up would work just fine for two channel music. Well, I've been heartily disappointed by two channel listening ever since. The brains of the system is an Integra (Onkyo) DTR 6.2 receiver. Speakers are DefTech all around. Here's my question . . .

The 6.2 is 100 watts/channel at 8 ohms. The mains (BP30's) have a power handling capacity "exceeding 500 watts." The 6.2 has pre-outs. Can I add a separate 2 channel amp only to the main r/l pre-outs to beef up the sound of the mains for 2 channel listening? (and leave the balance of the speakers attached to the receiver's amp for HT). I don't want to switch speaker connections when moving from HT to stereo. I have heard from several sources that the BP30s are very power hungry. If I can do this, and up the watts significantly driving the mains, will I see an improvement in sound? Particularly, I am disappointed with the thinness of the bottom end. Not a problem with HT due to the addition of a sub, but I prefer to listen without a sub for music.

If all this makes sense, and is possible, I would like recommendations for amps. How much power? What should I audition? My budget is more beer than champagne right now.

For what it's worth, I listen to 75% vinyl -- all styles of music.

Please don't flame the DefTechs or Integra, or tell me to scrap the system and start over. That's not very helpful and not possible right now.
It's a simple matter to connect a two channel amp to the preamp outs from the Integra. If you want to you could even connect another pair of front speakers to the new amp and leave the ones that are now conneted to the Integra. You can switch them off with the speaker on/off button when you want to play the new ones. The amp in the Integra will not be used when driving the new front amp with the pre-outs so it could still be used to drive other speakers.
As far as amps go, there should be plenty of good used amps for sale here within your budget. What did you have before?
I think your idea is great. Changing amps will without a doubt help. Your only consideration is do you want the center channel to have the same amp as the left and right? Do you use theater much?

I would advise borrowing an amp or grabbing a demo from a dealer for a night. See if it makes a difference. I would avoid tubes or class A rated amps if your whole family is going to use the theater and abuse or leave the amp on.

You might even want to consider a nice little 3 or 5 channel amp. The sony, marantz, B&k, Anthem and more all make nice 5 channel amps that you should be able to pick up for under $1000
I had the same problem: my Denon receiver (2802) was simply not cutting the mustard for 2-channel.

Ended up buying a Plinius integrated amplifier. Here's how an integrated (w/ phono) can solve your stereo vs. HT problem:

1) Turntable is connected directly to integrated,

2) Main L+R preouts from HT receiver connected directly to integrated,

3) Main speakers connected to integrated,

4) That's it!

When you're listening to vinyl, the receiver is not even turned on. When you want to pop a DVD in, switch the integrated's input* and it will function as a power amp.

The bottom-line is that the speakers are only connected to the integrated amp.

Check my system to see how I do it.

* Many integrateds have a 'HT pass through' or 'pre-amp in' which allows you to bypass the integrated's preamp function and go straight to the power amp section. Examples include the Plinius 8200, Musical Fidelity A308, Arcams, Primares.