I own a SvS PB12+ right now and I m thinking of replacing it. Would a PC13-Ultra be a upgrade or downgrade? I ONLY use my subwoofer for Home Theater movies, NOT for stereo at all.

20-39 Plus (close equivalent to your PB12 Plus)
http://www.hometheatershack.com/forums/subwoofer-tests/5767-svs-20-39pc-20-hz-
tune-plus-12-3-a.html

PC 13 Ultra
http://www.avtalk.co.uk/forum/index.php?t=msg&th=24667&start=0&rid=14&SQ=1216241881

the PC 13 Ultra can go louder in the lower frequencies ... yes i think it would be an upgrade

I own a SvS PB12+ right now and I m thinking of replacing it. Would a PC13-Ultra be a upgrade or downgrade? I ONLY use my subwoofer for Home Theater movies, NOT for stereo at all.

12<13

Plus<Ultra

Downgrade?????? Impossible

I would say you'll be surprised by the difference. The Ultra has a different feel than the Plus.

Based on what I've read on many, many forums, the Ultra 13 would be a major upgrade.

I own a SvS PB12+ right now and I m thinking of replacing it. Would a PC13-Ultra be a upgrade or downgrade? I ONLY use my subwoofer for Home Theater movies, NOT for stereo at all.
are you reaching the limits of your sub now?