Please recommend some active speakers

I'm looking to pick up a pair of active speakers. Space constraints dictate that not having to purchase an amp or receiver is highly beneficial at the moment.

I was looking at the Paradigm Active 20 and 40 models. Can anyone recommend any other good active speaker models in this price rage? I thin the Paradigm 40's might be just out of my price range so something closer to the 20's would be best. They should be bookshelf monitors. Looking to buy used.

Many thanks.