SL3s were my first good speaker in 1995 and served as my primaries until 2011 (Dyne Sapphires, then Raidho D2s, keepers). I had plenty of amps and wiring changes over that time and used decent copper wiring.
I'd definitely recommend horizontal bi-amping if you can do it. I think you can use a splitter on L and R outputs to enable inputting to different amps but each will get the entire audio spectrum (since no active crossover first) which will work fine.
Good luck. I seriously loved my SL3s (paired with a Velodyne); that's why I kept them so long . I still have them in another system here at home.
