I have an 8x4 table running 170 oz/in steppers.
Some of the best advice I can give you is to look at Millmans thread on his build, I believe it to be one of the best write ups on here.
I can get 6500mm/min rapid rate on mine, the fastest I run it for cutting is about 2500mm/min because of fast direction changes etc.
You will also need a signal generator which works with the software you intend. Candcnc do a good package which contains all you want. The price on the e-bay site is very very cheap. I think you get what you pay for.
Have a look at torchmate and flashcut aswell.
A good cad program is also needed. I think to get anything worthwhile you will be spending a couple of grand to get all the bits.