Hi, a couple of months ago, I bought myself a Sieg X1 and CNC'ed it. It was quite a lot of effort researching and sourcing the motors, the motor mounts, the drivers, the PSU and the CAM and machine controller software, and it ended up costing me a lot more than I expected - making some of those prebuilt CNC machines look like good value.
I am already considering a larger machine as I want to be able to make bigger parts and to make small ones is much less time. This time round, I am considering building from scratch, probably using parts from marchant dice, but even my initial cost estimates are rather scary. I have already bought the parts for one axis, and while they are of lovely quality, they did cost more than my manual X1!
I am also more electrically than mechanically skilled, and so am finding the prospect of building from scratch a bit daunting, but atleast I have a CNC mill and a lot of software to help me cut parts for the new machine - do you have access to the tools you'd need to make your own mill?
I'd also recommend that you budget at least 300-500 Euros for tooling - vices, collets, mills, measuring devices etc eat up cash like you wouldn't believe!
Also if you're going to be doing a lot of aluminium, you should probably consider a coolant system - this means an enclosure, which is a whole other adventure!
Best of luck, whichever way you go!