That is the big question. I went the the Alesis M1 Active Mk2 self powered monitors. Mostly because I was in school for Audio Recording and Engineering and they had a pair of them there. You can find them here...
M1Active MKII Personally I love them, they are well rounded speakers, really loud if you need it, and not all that expensive. I believe they were around $300 - $400. I got them from Long & McQuade so I was able to do a monthly payment while I was in school. I'm actually thinking of getting another pair so I can have surround :)