Good luck with your purchase brendelac!
I am the one jb mentioned that had just purchased a 18.0C, and I am about 5 to 6 weeks away from getting it delivered.
I came very close to getting a XS30, so we are moving in opposite directions. I would of definitely have recommended the second 15.0.
I think a second 15.0 would of been all that you need, and filled out your room nicely. Easier to do with the 2nd sub being the exact same one. As well, as good as the PSA subs are, I think you are taking a step
back in quality. Only my opinion, but the quality of cabinet, amp, and drivers to me seems to be higher with Funk, which is why I went with them. You could
probably get a second 15.0 for not much more than the XS30, especially if you get it delivered in the the Lower Mainland, and pick it up on your next trip down. Might be worth a call/email if not too late.
Let us know what you think of both, would love to hear how the 2 compare when you get the XS30. Please keep us in the loop!
When are you getting it?