Have you built speakers before ?
I'd imagine everything has to be spot on to build decent monitors.
Good tips from morbid, it's always a good idea to go secondhand and pick up some better ones.
Good cheap ones though used to be Fostex, Alesis and Krok's. Not sure if they're still the best around for that price range though.
I personally wouldn't advise listening in shops, the room will be totally different to your studio room.
You can generally get a good idea of which are more highly regarded if you look around on the net for long enough.