My first question is, are you sure about Slot A?
To be up front, pverclocking a slot A is much more difficult than overclocking the Socket A cpus. I don't know your level of technical know-how, but to OC a slot A athlon, you generally have to crank open the case it's in and attache a "gold finger" device. That device is a PCB board with dip switches that chance the frequency settings and voltage settings of the slot.
Also, Slot A is a dead end move. There is no upgrade possibilities. Socket A has life in it. And it's TONS easier. Connect L1 bridges and then set your Mobo to change everything. (assuming your board supports OC)
So, I suggest going with Socket A. It's cheaper too.