I am not familiar with the PMC sub, but if you look for the most fun factor in your cinema I think an SVS would be a wise buy.
But, please be aware that you have a classic REL subwoofer, which is no longer produced! REL has american owners now, and they dont care much for audiophiles, and stereo. They would like to have a piece of the home cinema market and has given up the subwoofers for the average audiophile. The two largest models are still produced though.
REL Strata and Storm models wil be highly sought after in the market now, and prices are likely to rise because these are very very good subs, so I really dont know what you should do.....
I really think you ought to try the Strata for music also, but thats just me.....