I ended up going a bit different due to circumstances that came up. I DID go with the 600C center channel, which is an absolute BEAST of a unit, and I would highly recommend it to anyone...just ONE warning: it is HUGE (phrasing). It is, quite literally, the size of a floorstanding speaker on its side. I am fortunate that my HT room is MINE so my wife says 'get what you want'...but if there's any Wife Acceptance Factor needed, you will want to run that by her/him
As for the mains, I got lucky and found a used pair of Goldenear Triton 3's a short drive away that I got for $1000 Cdn (about $750 US) and man am I happy with them. I always wanted Goldenears and now that I have them up and running I can say, in MY opinion, I agree with the reviewers that say these things sound like $25,000 speakers that you can get for $4000 (Or in my case, $1000). SO, unfortunately I can't help on the SVS vs Paradigm argument....but I can tell you I was leaning more towards the Paradigms in that scenario. Just the best CC where SVS doesn't really have a knockout CC.
If it helps, should you decide to go the SVS route I personally don't think the ULTRA's are a huge upgrade, they're pretty equal, from what I've read. They may have fuller bass BUT they're very finicky when it comes to placement, and you have to have just the right room for them because of the included subs. If your room isn't open enough, then you're stuck with muddy bass because you can't place the sub where you want. I think you're just better off getting Towers with a good SVS PB2000 or PB3000 if you can.
Hope that helps.