Can anyone recommend an amplifier/DAC combination or seperate devices for around $400 total, to pair with the PS500s? I've been looking at the O2+ODAC, aswell as the TEAC UDH-01 (mixed opinions on that one), but can't seem to settle as there's always one thing people dislike, makes a decision difficult. Size does not matter (home use), however I'd need USB input or spdif.
I don't know specifically for the PS-500, but the Musical Fidelity V-CAN-II is something I can recommend very highly (it plays nice with the RS-1, but then again, everything does!). VERY quiet amplifier, and that's basically the selling point imho. Perfect channel tracking (at least on mine), no bg noise, it's just completely out of the way of the signal. And that seems to work pretty well with the RS-1 (and any other dynamic can I've tried). So I assume it would work out very nicely with the PS-500.
I think Little Dot amps are also popular, but I haven't tried one.
Regarding the D/A converter - what are you hooking it up to? A computer? Can you just add a soundcard to this computer? Would be a lot cheaper, get you more options, and so on. In fact, I noticed that the X-Fi HD USB is back in stock on Amazon, and I would probably just get that either way (you get DAC, it has a headamp (no idea on quality/features/etc), phono preamp, DSP features, etc - it's like $80 too, very good deal!), and the V-CAN will bring you to just under $300.
IME, the PS500 is slightly (1-2dB?) more efficient than the 325is making it even easier to drive.