I know its not exactly about keeping the cost down, but it is important: make sure u have enough fans in your computer, 3 case fans might not be enough..(I need about 5
And about the fx51......yes, its a great processor and all that, it has 64-bit processing, great for gaming, yata-yata.....but 64-bit support in O/S is not very widespread, and until that becomes a little more common, you can only reap some of the benefits of having a 64-bit processor. In fact, if you wait and get the fx-53 when it comes out, there might be more support for 64-bit by that time.
 and you should be able to get the same amount of faster RAM for the same amount or less....$150 for a gig of...was it 2300?( maybe you ment 3200...?)... sounds a bit expensive. esp. considering there is at least 3600 by now. [/edit]