Those levels mean nothing.I really love the clarity of the SB-4000 but I really have to crank it up match the output level of the PB-3000.
I'll say that again. They... mean... nothing. There are so many variables in calibrating a system, and those are different subs with different amps, drivers, enclosures, designs. If you had to turn the 4000 up to +10 I'd be concerned that something was wrong.
My room is about 20x25 and my SB-16 Ultras are at -12 and -13. That's just the setting that's needed. Nothing more.
Ask @John Dirk about the SB-4000s. He has a pair in his HT. 20x30 is a pretty big room, but not much larger than mine, which is also open somewhat, and my SB-16s never even break a sweat. I was hoping I'd (along with Dave Upton) finally convinced you the common misconception about sealed subs is exactly that, a misconception. A truly capable sealed model can and will match a ported one in every meaningful way, and exceed it in overall sound quality. You can energize a room cheaper with ported subs, but you can do it much better, though more expensively, with sealed ones.