You will definitely want to join a pool if you have a lot of hashpower. How much do you/are you going to have? Mining solo isn't going to get you very far anymore finding a block and pools pay consistently. BTCGuild is good, but I've been on BitMinter lately because they have lower fees, which is something else you want to look at.

Check out this link:
https://en.bitcoin.it/wiki/Comparison_of_mining_pools