I have been looking for a 2nd CNC machine. I already have a shopbot PRS Alpha and want a smaller, 2nd cnc machine for 3 reasons.

1) I want a 2nd CNC machine to be working while the shopbot is busy.
2) I would like to do Aluminum once in a while.
3) I like building CNC machines

I used the shopbot to build a Joes2006 and that was fun, but that machine flexes way too much for my tastes. So, I was thinking about building a 2nd one. Saw the K2 2514 on E-Bay, and thought hey, theres an all aluminum machine for a reasonable price. but then after looking at their site, I really want a 3925G. I like the rail system a lot better and it just seems to be a much more sturdy machine.

So, I got a quote from them, and after all was said and done it was going to be $6500 without motors and controller.

I'm thinking to myself, people cut aluminum on the shopbot every day. Why not just build an all aluminum machine myself. Sounds like the rails and ballscrews are going to cost in the range of $1300, and even if I had $700 in aluminum, it seems like that machine could be built for about $2000. The overall design looks extremely simple from the pictures. I would probably change it to a rack and pinion (saving a lot of money on screws), and have 2 motors on the X axis.

What am I missing? Anyone else done this with success?

Thanks!
Scott...