For your system setup, you want a good quality active monitor. Control everything from your 'puter as you do now, no receiver required. You may benefit from a usb sound card, but maybe not. Take a look at this to start:
These are available online or at your local Guitar Center or similar musician oriented retailer, not hi-fi shops. They are great values, and provide some seriously good sound. I suggest those as a start because you could get away without a sub with them.
The JBL are all about the sound, and less about aesthetics. has some active monitors in pretty bamboo cabinets if you want to check out something prettier, and they even have remote control.
Sorry, not really providing reveiver advice, but for what your shooting for (improved sound), I think that this approach sidesteps the receiver requirement and gets you into better sound for similar or less money.