Maybe you can get a good motherboard/Cpu bundle from newegg. If you want to stick with the Phenom processor, I'd go with the motherboard.
Asus Sabertooth is a great board, AM3+ socket so if AMD gets their stuff together with their FX line that gives you the option. 990FX chipset also gives you SATA III support. As it is right now, you're better off sticking with your Phenom II for the CPU. Wait for a stepping revision before going with an FX. The recent Bulldozer releases, FX-4170 and 6200 were not stepping revisions.