Godaddy often provides promo codes that let you register domains for $1 a piece. This is only for the first year of course, but I suggest that you use google to find more $1 domain promo codes and get them as cheap as possible.
Actually, a domain name does matter when it comes to search engines, but the service provider doesn't.
In other words, it's important that you register/buy a keyword rich domain name, but it does not matter where you do that (godaddy, moniker, network solutions, dynadot etc.).