Stephen,
Arggg! Sorry to hear that. That's great news for whoever got them, but it sucks for you. However, more opportunities will come along.
If that sub is in good shape, then I'd say get it at $200. There are others on the forum that know more about the details and history of the SVS cylinders, but I'll give some details to get you started tonight. You can view some of the earliest info on the PC-Plus line at
this link from SVS (start at the bottom and work your way up). The PC-Plus line started in 2002. Since then, I know of two changes. First, SVS developed their own woofer (the 12.3) and put it into the design in 2006. Second, from what I've seen on this forum, the PC-Plus amps now include a single-band parametric equilizer - though not shown in the SVS pictures, a member here (Bluesmoke) put up pictures that
showed it.
I don't have a feel for how much better the 12.3 woofer is than the original version. I can say that the PEQ came in handy on my PC13-Ultra. However, that said - are those two items worth an extra $700+shipping? Not to me! Again, if that sub is in good shape, I'd get it. I'd say that it's worth the drive to check it out. I just hope that you get good gas mileage.

If you can get the seller to send you photos of the sub first, that would be nice. That way you could see if there's any obvious damage that would keep you from wanting to make the drive.
Adam
EDIT: BTW, you can buy the
12.3 woofer from SVS for $169. So, even if you really want that woofer, it would still be cheaper to get this sub and upgrade.
EDIT 2: You can view details about the 12.3 woofer and it's debut at the normal SVS news link
here. Just scroll down to the April 14, 2006 entry.