Here's my final suggestion:
Spend $60-70 on some decent headphones like some Sennheisers or Grados and then just buy any old logitech, Klipsch, Creative or Altec Lansing 2.1 speaker set for your computer when you don't feel like wearing headphones. Don't worry too much about the speakers because all the 2.1 sets in the $20-40 range aren't that great. You can use the headphones when you want good sound.
Some headphones to look for:
- Sennheiser PX-100 ~$50 or less
- Sennheiser HD models like the HD-465, HD-435, HD-205 etc. I don't know how good they are but I'm sure they're ok. You can find a bunch ranging from $40-70 I think.
- Grado SR-60 (~$60ish I think)
- Grado SR80 (~$70-80ish I think)
That's it for my knowledge of inexpensive over the ear headphones. The PX-100s are pretty good for the money, but I think the Grado SR-60 or SR-80 are worth it if you've got a little extra money. I'm sure there are other options to consider like Sony or whatever but I don't have as much experience with them.
In any case find a decent pair of headphones for your gaming or when you really want to get in to the music and just get some inexpensive speakers for their "utility."
My $0.02.
edit: well you coulda specified no headphones earlier. In any case, all the $30ish 2.1 sets are about the same and none of them are very good. Just get whichever looks coolest