Advice on sub for DCM Time Windows

I have the DCM Time Window 7's w/a B&W ASW 750.
The Sub is a great compliment to the speakers it fills up the room and lows w/out overpowering anything, you feel the base, the house shakes, but everything else sounds great too.

I am driving the speakers w/a pair of Carver A500x amps in monoblock configuration

Yea BW makes great subs, go for it!

Have an opportunity to pick up a used B&W ASW 1000. Would this be a good match?

Vandersteen should be a great option. My first pair of
"hi-fi" speakers were Time Windows.