Which receivers have decent stereo performance?

Well if you can use the Yamaha as a preamp for now.I would use a seperate amp or amps for the Soliloquy 6.3s.The speakers are so efficient the Yamaha doesn't sense a load so it want put out any real power.
Two Monarchy SM-70 monoblocks used ($700) will give you an enormous improvement!Even a Van Alstine 120 D will take them to a different level.You can get some Acoustic Research directional interconnects from bestbuy.com for $13.00(shipping included).Parts numbers are AP0-30 or AP0-31..depending on lengths.Try to stay with the shorter lengths if you can. These interconnects do not know their place when it comes to price verses performance! Theres a Van Alstine 120D for sale on Audiogon right now! $450.00 plus some AR ICs will put you under $500.00 total and the improvements will be huge!

Trust me on this one you want be disappointed!
Good Luck!

I would go with a Marantz or a denon. both are pretty good at music. A friend of mine have almost the same system set up, I have a Yamaha RX-V800, and he has a Marantz 7300. his sounds much better for music

I'd second Gmood1 suggestion of adding an amp. I have the RX-v2200 and was not happy with the 2-channel sound either. My Paradigm Studio 60s are not very efficient and the Yamaha didn't have the umph to drive them. I added an Odyssey amp and was amazed at how much the lows and the mid-range opened up. Add the amp, not another receiver!

If I follow Gmood1 advice, I need to unplug/plug the speaker cables when switching from stereo to HT from amp to receiver, right?

Instead of wasting money in a bigger receiver, the suggestion of a separate amp make marked impact in the performance of Soliloqys and will definetly set you square in the path of better sonics, in the future. I might call the purchase of the 1K receiver as a temporary solution, which in the long run will force you to squander more money in the selling and upgrading game. All receivers, used below 1K and the one you are using were built to fit an economic formula in the minds the company, a separate amplifier, as the Monarchy that were suggest has less compromise in their production than a mass produced receiver....and if there is a compromise, it was done accounting the clientele of the buyers who would purchase their amp....people who can be very demanding of the quality that the amp will produce. Simply, go for the amps.