depending on your budget what you really want is some edirol speakers, these are the kind of things that artists use, they are small speakers, similar to bookshelfs, but they have an in built amplifier that is really good, also they run to a 3.5" jack which is the standard output via every souncard bar none. In term of power which i dont think is a very good judge of speaker ability they are rated at 25W, which if you consider that constant power is bloody good. I hooked a pair up last year with my mini ipod before investing in some soundsticks, only because i wanted a nice subwoofer to look at. Anwyway i'm missing the point, don't be put off by 25W, m front 2 ruark speakers that i run with a £3000 Naim amplifier set-up run around 100W and they can crack the plaster (which they have done 3 times) if i get fiesty with the amp. The price well its round £90, but i saw some go for £65 on eBay from a well known seller. Cheap if you compare to the £2500 tag on my Ruarks lol. Hope this helps and i will try to get the cose for you soon as...
Cheers
Mattpower