As Hugh said, they seem to enjoy some oomph behind them. I also find they are very picky about positioning. If you didn't try it already, don't toe them in towards you. They also seem better in a larger space than you might have expected for a monitor of it's size.
For my TB2's at least, they work better when treated more like mid fields, than near fields.
And yes, if you don't like the sound of used ones, then you'd run mile if you heard a brand new pair
Just my 2khz worth! Paul