Best integrated for $500?

With the Titus 202 in a small room you have a lot of options, as you don't need much power. I have the same Titus model in my office powered by Boulder Cable modified TEAC tripath amp (30wx2), which is more than enough. Interestingly, I also had the Creek OBH-14 for years, and while living in Europe for two years, my system consisted of the Creek with Rawson gainclone, and my Triangle Titus 202. Which brings me to a question; why integrated amp when you have a passive pre built into the Creek DAC? On the other hand, the Creek DAC may not be up to par with with your system potential. I found it very sensitive to jitter, BUT using a Monarchy DIP Upsampler made a day and night difference.
Knowing the speakers, and how much importance the quality of the source makes with them, I 'm tempted to ditch the creek and recommend a used Peachtree Decco II (integrated tube hybrid with a Sabre DAC)- there is one just listed here today for $580. Or find a good Tripath or a lower powered tube amp that has high enough impedance to work with a passive pre- and squeeze a Monarchy DIP into the budget ( go for about $100-140 used on Audiogon).
My second system evolution has gone from system 1: PC-> Trend USB to coax converter ->Monarchy Upsampler -> Creek OBH-14-> Rawson gainclone -> Triangle Titus 202; to system 2: iMac -> HRT Music Streamer II -> Luminous Audio Axiom Passive pre -> Boulder modded TEAC Tripath -> Triangle Titus 202. Not entirely fair comparison as amplification and rooms have changed, but there is no comparison in how much more resolution there is in my current system, as well as soundstage and imaging. No harshness, nothing bright. Go figure, the HRT streamer goes for $150.
Sorry for causing you more confusion... but when you sort it out, it sure might be worth it in the end.

I would think that a used Creek integrated amplifier would be a solid choice. A while back I had 4240 driving Spica TC-50 speakers and it was a very good combination.

Rogue make a very good-sounding, very well-built integrated and I bet you would be very happy with it over your Onkyo. It's the tubes--they just make music so liquid.

Even tube amps don't all sound the same, though, so here's another suggestion, just in case you get the chance to compare: an Audio Space AS-3i. It sounds lovely too, but different.

And of course there are more.

Asking your question on this forum is sort of like asking a fashion designer forum who makes the strongest shoe strings.

I think you need to look (listen) hard at your local brick and mortar electronics store and you may be pleasantly surprised by something with a household brand name. You might also be surprised how well your existing Onkyo performs against audiophile brand name components.

All that is not to say that I don't really appreciate the cool factor of some of the components already suggested in this thread. I just think that when you want excellent amplification for low investment, the efficiently mass produced receivers are the way to go.

Or, you could buy a Nad or Arcam:).

Have a listen to the Yamaha A-S500? WhatHiFi had only good things to say. Buy.com has a great price on it. I would also check out the Rega Brio 3.