Use anything with POW-r ... particularly the noise shaping curve #3. To my ears (and many others), it's the best-sounding software dither algorithm. I didn't know anything on a PC used POW-r, actually.
The IDR dither on the Waves plugin bundle is pretty good too, and Wavelab uses UV22HR, which isn't bad either.
-Matt (uses POW-r in Waveburner on a Mac)