+1 to @audiorusty on comments about JL Audio "e" series (I have an e110--superb sub for limited space) and separate crossover.
My previous sub, though wonderful sounding (SVS SB-1000) has a rather non-transparent, poor-sounding low-pass output crossover. Instead I got a very good quality Marchand electronic crossover and no longer relied on the sub's crossover. Big improvement, plus the fact is relatively few subs even have a low pass output (RCA pair), much less a good sounding one.
As it happens, my e110 is one such sub. But I found it more convenient to continue using the external crossover than the JLA's crossover output, due to a pesky ground loop.
If you don't happen to have an integrated or receiver w/quality filtered outputs for sub + mains, an external crossover is the way to go.
My previous sub, though wonderful sounding (SVS SB-1000) has a rather non-transparent, poor-sounding low-pass output crossover. Instead I got a very good quality Marchand electronic crossover and no longer relied on the sub's crossover. Big improvement, plus the fact is relatively few subs even have a low pass output (RCA pair), much less a good sounding one.
As it happens, my e110 is one such sub. But I found it more convenient to continue using the external crossover than the JLA's crossover output, due to a pesky ground loop.
If you don't happen to have an integrated or receiver w/quality filtered outputs for sub + mains, an external crossover is the way to go.