"When you turn the sub on, the LFE channel no longer goes to the mains. That should be the only real change. There will be a need to recalibrate the system to get the sub set to the right level, which is probably the first place to look."

When I turn on the sub, since the LFE is only going to the sub, what frequencies are going to be going to my mains and center for their built-in subs?

"Another thought: unless you are using 7 Stereo, "
(which I will be doing as soon as I get my speaker cable in the mail from eBay)

"the side and rear surrounds will rarely get a lot of bass, so hooking a sub to them may not be a very great use of that sub. "
I dunno, the way I have it at the moment, with one PSW10 going speaker level in and out to the BP2X's in the rear as a 5 channel system, the PSW shakes the couch next to it pretty well...what are your thoughts on running speaker level in and out but only using one channel per sub? (one for left and one for right?)

"It may be more effective (and simpler on your speaker wiring) to use a splitter from the 950's subwoofer output to run line-level connections to both the PSW10 and the Velodyne and then run the side and rear surrounds as "small" with an 80Hz crossover or so."
That makes good sense, but it just seems that I lost so much from my Mains and Center when I set the sub to "On"

" That way both subs would handle the LFE and would pick up the occasional low frequency from the surrounds. Just something to think about..."
But would my built-in subs in the Mains and Center be utilized like they should be? By that, I mean will they get a full range signal? If, by setting the speaker to "Large" always means that they will get full range signals, then going with "Y" adapters and setting all three powered subs to run from the single LFE Out, and the speakers with the built-ins run with speaker wire inputs only sounds like a winner...

I am confused by this all, as, even when the speakers are set to "Large", then I still have crossover points to select, which confuses me....shouldn't it be getting full range when set to "Large"? Why even have the crossover option in that case?

Or is my 950 just so old and out of date that I will have to live with it until I can afford to upgrade?