chuck makes some really good points... sounds like you know about what you want to do with it, now you need to figure how precise you need to be... is .002" good enough or do you need .0001"... how much detail are you looking to have in your finished parts... and just how precise do they need to be.. for most wood stuff, i think .001" is WAY good enough... but for aluminimum, maby not so good, depending on what your making... personally i went with a real router motor.. a porter cable... but i got lucky and it was handed to me along with the following quote, "here, i thought this might be something you could use, so i got you one".... the other think to think about isjust how fast are you gonna wanna cut.... if your looking for super fast cuts and lightning fast rapids, get ready for some sticker shock, cause servo systems, both the motors and the electronics to support them, are not cheap... if your like me, and speed isnt as important as just getting it running reliably, and money is a real problem, then bipolar steppers might be a better choice... i picked up 3 500oz-in 4 wire bipolars on ebay for under $200 usd... im building my own drivers and computer interfaces, so im saving a bundle there... you might think about going with a kit.. i have heard that there are several good choices, they come with the drivers and motors, and i think some even come with the powersupply....
another thing to think about is leadscrews, just like chuck said, there are options here, if you wanna go fast and be accurate and repeatable, ground ballscrews are the way to go, but here again, the mechanic in Mad Max said it best, "Speed is just a question of money, how fast do you wanna go?"
my machine has a theoretical step size of .00025"... thats waw more accurate that i need... my original plan was to gear this system up to double the speed and half the accuracy... but that'll have to come later when more $$ is available....
my best advice, sit down, figure out what you want and what you can afford, and then start looking for the parts and stuff that you need.... but be realistic about what you want to do, vs, what you can afford.. oh, and keep on asking questions here, cause these people know thier stuff, i have learned so much from just sitting here and reading.... its a really amazing source of information...
Grizzly X3, CNC Fusion Ballscrew kit, 3 500oz-in bipolar steppers, 3 203v Gecko's, Linear power supply from Hubbard CNC, Mach 3, BOBcad Pro Art V22, Rhino.