You should ask the guys at the shop if you can take the speakers home to test in your studio(or whereever) put down a deposit if need be. They should be used to people not being able to judge quality in shop and should have some system worked out - just say your a pro and qulaity is important. IF your cheeky try and take home a few at a time in different price ranges.
Also you want to choose a speaker that doesnt only sound good but also displays mistakes well (ie doesnt still sound good with shit playing through them) otherwise youll likely have problems.
Check for these too, as was recommended them myself, though you'll need a nice amp
http://www.quested.com/p/h108.asp .