Shim,
If you buy cheap speakers now you will end up replacing them later.  I used a pair of M-Audio BX5a speakers - even on gigs at first.  They are great sounding and ran about $300.00 for the pair at Guitar Center.   Like a previous poster said - there are others - best for you to go listen to them in the store first.  
I have a set of Klipsch and a set of Bose speakers that are actually meant for computers and it was a surprise how good they sounded with my Yamaha keyboards.  They were both under $200.00.  I ended up not using them very much after I got the M-Audios.  
Good luck with your search.
Hammer