Companion post to my earlier one re: linear guides...

I'm about to just jump into build mode after a year of lurking, reading, learning, and overanalyzing. The new machine (my first CNC) will be a nominal 8'x4'x12" 3-axis w/906oz-in steppers, <125# gantry, and a welded steel frame (with a few epoxy-bedded bolted connections). 3kw Chinese water-cooled spindle.

The challenge is to build the most machine I can for the money. Target is acceptable quality for a small production shop working in wood, foam, acrylic and occasionally some aluminum sheet. I'm not trying to mill steel, nor make NASA-quality parts. At the end of the day, however, I do need to get usable cabinet parts off this thing.

I've read so much I'm bordering on overload. When it comes to drives, I'd really like to stick to ballscrews, but they start to become cost-prohibitive when they get big. And frankly, I'm afraid of screw whip. I tell myself to just simplify and go R&P, but don't know a lot about the whole split pinion thing. Belt seems easiest, mechanically, but after reading a great many posts, I'm convinced I'll build myself a giant slingshot, with so much spring it would be unusable. The belt would be my first choice, because it seems simple and elegant. R&P would seem to follow, if someone could make the split pinion thing simple for me, and the ballscrews would be ideal, if anyone has surplus that they'd like to donate to the cause

I know there are a lot of calculations to be done, and a lot of information not given. I'm looking for more seat-of-the-pants experienced advice. I don't so much need a best-in-class machine at the end of the day, but I do need to avoid spending a lot of time and money making a piece of scrap metal.
Thanks very much in advance.