Craig ("Craigsub") organized a showdown between EP500 and a single SVS Ultra (don't remember if it was a PB or PC).

Haven't seen anything between a 500/600 and a 2-driver 900 watt Ultra, but that would sure be an interesting battle. I would bet on the SVS but only by a small amount, and that would depend on whether you ran the SVS in 25 or 20 Hz tune.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8