I would also recommend getting the matching CS2 recommended by Polk audio. I run a pair of Polk RT3's for my mains and I purchased a less expensive non-matching center for my system and I've regretted it ever since. Now I'm married, 2 kids, doctor bills, etc, who knows when I'll have cash to finally get something I should have spent a little more money to get the first time.
Nothing beats doing it right the first time!