Looking for a subwoofer
 

I am looking for a subwoofer in the 100-200 price range. It has to to keep up with 2 quite loud bookshelfs that have 6-1/2" woofers with 2" tweeters. 4-8ohms rated at 60 watts

Any ideas? I dont know to much when it comes to them.

It really depends on how much you want to spend and what bookshelfs you have.
If you have cheap ass bookshelfs, there's no need to buy a $600 REL Subwoofer.
If you do have a nice pair of speakers, it might be worth investing in a nice sub.

Nevertheless: If you don't plan to use your setup for films, you're probably better off with a set of nice floorstanding speakers. This usually sounds better for music than most subs :)