Those kits look attractive, but are underpowered (low-torque steppers, low voltage PSU, inadequate drivers) and the TB6560-based version also has the problem that all the electronics is integrated on to one board so when one of the drivers goes pop (these versions do...) you have to scrap the lot.

The electronics is not the right place to start. Although you have talked about the materials you would like to cut, you haven't mentioned cutting area which is a major design driver. And although everyone would like to cut aluminium, that's a big step in rigidity and accuracy over and above what's needed for wood.

Give a bit more detail on your machine needs, and look through the build logs on this site. It's a bit of a trawl through a lot of threads, but there's a good chance that someone has built a machine similar to the one you would like, and that will give you a realistic idea of the art of the possible. Lightweight commercially- or kit-built machines might work for you, but they also have limitations and you need to go down that route with your eyes open. I'm not saying don't, just be aware of the compromises you are making and decide realistically if that's for you.

Ask questions and listen to the answers - there's a lot of experience on this site from people happy to help.

Just as a stake in the ground, thinking about budget - my roughly 1500x750 cutting area machine that will probably tackle aluminium although only used for wood so far cost around £2500 in materials, ballscrews, guide rails, electronics, etc. It all depends on where and how you source materials and your own machining and assembly skills and facilities.

But good luck - it's great fun building a machine like this! Just be realistic