Center speaker for Polk RT30's?

[acritzer]

I have a friend that is getting into upgraditis. He currently has Polk RT 30's towers for L/R. He thinks they are an older model (I don't know much about them). I've been giving him a bit of advice based on my readings and my speakers.

So...would a CS1 or CS2 match up with what he's got? Or, can you possibly offer something else that would work well? Budget probably under $150?

Add-on question. Sub recommendation? He picked up a 10'' Yamaha (don't know the model), isn't happy with it and is probably going to take it back. He's looking at a few Polk subs on Newegg. I know Polk isn't all that great for a dedicated sub, but they have cheap prices.

Thanks.