My computer setup is in the living room (since there are no other rooms besides the bedroom kitchen and bathroom) so my computer setup is in about the same size space as your room. For nearfield listening powered monitors may be a good way to go to save space and hassle if nothing else. You can even plug a headphone jack to RCA direct from the computer into a pair of powered speakers like the emotiva airmotivs for example.
If you choose to go the way of an amp, I'd highly recommend SMSL on ebay. They ship direct from china and you'll pay a heck of a lot less for a lot more amp than the small daytons.
For passive speakers, my preference is the Emp Tek E41Bs. The E41B's are sold out, but emp still sells the E41's which should sound very similar. They're cheap, but the stack up against much more expensive bookshelves IMO. They're great for nearfield and come with port plugs specifically for near field listening.
There are a ton of good speakers out there for desktop so odds are you'll end up loving what you get.
I'll also mention, that while the size of the room is important for bass, you don't need a rated large or whatever sized sub. You're listening near field, odds are the sub will be extremely close to you and you're not trying to pressurize the whole room with room shaking bass. Unless you like dub step, rap, or techno music at head rattling volumes while you work don't over spend on the sub. Get something capable, small, and don't break the bank.
Cheers.