Personally from what I have been reading/hearing from our esteemed peers, the S2's have wonderful SQ especially if you are amping them. They would certainly be a nice upgrade for you, and for their approx $120 total price, would be excellent best bang for buck. Again though, you would probably want to be amping them (anyone chime in if I'm wrong about this).
They definitely benefit from amping, but mostly because they are so transparent. They don't need it, but you will appreciate the difference in sound if you have multiple amps/sources.