I have a pair of M-Audio BX5 D2 studio monitors hooked to my PC. I have Meelectronics M9 in-ear headphones, but I'm planning on getting a costlier pair of in-ears, maybe Etymotic HF5s.
Right now I just have the sound chips that came with the motherboard. I'm looking for a DAC that would work well with both speakers and headphones, preferably under $100 but up to $150-200 if there's a really good reason. I listen mostly to acoustic music (classical, trad. folk, etc.) but also listen to classic rock. It does seem like the sound from the speakers, while good, is a tad quiet unless I turn it up quite high.