For a nice 2 channel system, I would be looking at a
Motu M2 interface combined with something like a
Kali IN-8,
Presonus Eris E8 XT, or an
Adam Audio T8V. All of those speakers should have a good response, and decent bass extension. They are all powered, so you don't need to buy an amp. The Motu has a very high-quality DAC for the price. The advantage of these systems over the passive speaker system that are being suggested is that these will have a more accurate response. They will also have a wider dynamic range. Passive speakers in the same price point can't really compete in terms of sound quality. The disadvantage is this system can't really accommodate an HDMI source if you wanted to hook it up to a TV or something. For that, you would need a DAC that had an HDMI input and good balanced outputs. I am not sure who makes something like that or how much it would cost.