Amp for desktop system?

I'm in process of building a new desktop system for my home office and need to choose a standalone amp (not integrated) for whatever speakers I purchase. Any input would be much appreciated - I'm getting lost digging through the forum archives!

Details: Nearfield listening while at the computer (3 ft), small room, up against a wall/window, lower volume levels so the "first watt" principle matters a lot.

System will be PC Apple lossless iTunes -> External DAC/Pre combo(Beresford 7520) -> Amp(TBD) -> Speakers (TBD - Likely Totem Dreamcatchers/Mites, Epos M5, or Usher S-520). Music is all over the board, alternative, jazz, female vocalists, eclectic misc stuff.

Sonic preferences - I really value a spacious, airy sound with fluid vocals. Soundstaging is a priority (contrary to my layout, I know) and an open detailed sound is more important than pure dynamics, probably won't get played loud much. Tight accurate bass is more important than a deep low end or slam, esp with my small speaker choices.

Budget is $250-450, used gear here on audiogon is the likely source.

Any suggestions on what brands/models to consider? I get totally lost looking through the classififeds.

Am I on the right track with the rest of the components? Still trying to decide on the speakers but am leaning toward the Totem Dreamcatchers (4 ohm speakers) after demoing them yesterday.

Any help is much appreciated. Thanks!