Help finding a subwoofer

@ieales  Hi I do  get the line level and rolling off the main speakers.  This can ease up the main amplifier and not stress the woofers of the main speakers.  I did this with my bookshelf speakers.  But IMOH I feel large 'full range' speakers sound better run at full spectrum with dialed in subs, using the high level inputs (aka REL).  And totally agree two is much better than one for eliminating (or minimizing) room nodes.

I was very attracted to the iphone control of the SVS subs.  But I feel the REL Carbon Specials sounded much better for music.  It does take a bit of up and down adjustments to get them dialed in, but then you forget where they even are.

They go now used for more than I paid new.

+1 @winnardt about REL quality and sound.

As to the high pass filter @dynamiclinearity I agree there are pros and cons. Full range speakers and good amplification can handle full signal.

The quality of the high pass filter is hugely important in a resolving system, and I believe in not altering (DSP etc) the signal. It adds distortion. That's just my approach.  DSP for a sub? may be a good idea to tune to eliminate room nodes.  I was able to move my two REL subs around until I had minimal bass booming.  The addition of ASC bass traps (I found them used here) in the corners smoothed it all out.  Who knows, if I had subs with iphone controlled DSP I would have liked that, but I think in the end I prefer the purity of the signal.

Thank you for those great responses.