Craigsub,
You'll find the PB10-ISD to be HUGE compared to the tiny Cadence. Mac and I compared them, but not side by side. The 10 goes much lower, but doesn't hit like the XSUB. I think you'll be pleasantly surprised by the Cadence. If you're brave, unscrew the amp off the XSUB, and then take the amp off the PB10. Compare the two. Your jaw will drop. Those two subs running together may make a perfect HT/musical combination. Now to find the room for two subs.
Make sure to break in your Cadence. It's EXTREMELY stiff out of the box. Mine didn't produce the "boom" for a week. I didn't believe in "break in" time b/c of the myths on this site, bit then took Velodyne's word for it (check the manual on all their subs). After the break in, the sub really sounded much more like a HT sub, but still only goes down to around 28Hz.
BTW,
What is a Craigsub? Craig made car audio equipment years ago. Any parallel there?