I think those KRK's are your best buy around 150 bucks, I'm definitly not into Behringer, besides being cheap, they're crappy too. 'Good for the price, but not if you need to buy new ones 2 years later. I know I exceed budgets here, but to set an example, a Genelec 1031a set will cost you a $2500( not even starting on the new 31 model ) but will practicly go a lifetime if handled with care. You'd need to buy a hell lot of truths for that amount of rendement ( timewise ), but a lot less KRK's ( KRK is underrated and actualy favoured by lots of studios ).
If you're looking into buying something nice from ebay, look for a Soundcraft Absolute 4p (active) set. These are very good active nearfields ( a pleasure to the ear, does not fatigue on the long runn ) for domestic little bedroom studios and should come in cheaply.