I'm guessing the R300's are just a newer version of the R30's, except the port is now in the rear instead of the front. I have the R30's as mains and the matching R15's for surround and surround back. Polk reccomends the CS1 as the matching center, but actually the CSi25 is the matching center. I looked on Friday and outpost.com had the csi25 for about $70 + shipping, but you can easily find them on ebay. I originally purchased the CS1 for a center, but after reading some reviews on the CS2 I sold the CS1 and got the CS2, since it uses 6.5" woofers instead of the 5.25" woofers, and it does sound much better, even though it was $100 more. I got the CS1 for $100 on ebay, and the CS2 from the same person for $200... both prices were $100 less than retail. You really can't beat those speakers for the money. I would get the matching bookshelf speakers too if you are setting up a HT system.