It doesnt have to be a gecko drives, I just mention those because anyone playing around with diy cnc has at least heard of them. A gecko G540 would give you all the drives and a breakout board in one simple package. Albeit at a cost of more than your complete parts kit.
I honestly dont care what hardware I get as long as I can run Mach3. Having the application specific control screen with a graphical interface takes a homebrew cnc and makes it operate in a manner very similar to my commercial cnc machines. As it pertains to this discussion the biggest benefit would be the direct interface of the software to the THC and the ability to tune the parameters on the fly.