1/8th scale brushless setup for my buggy.

I'd say the cheap way is the Castle Mamba Monster Max, Fiegao 9XL and on 4s, unless you can find a used Mamba Max setup for cheap, but if you have to go new, might as well get the MMM for the cost difference. If you want best bang for the buck go with the Medusa, its a much better motor than the Feigao and not that much extra $