Buyers guide - bang for buck - suggestions

I am looking at getting a CNC machine to do some things that my laser cutter wont do. 1) leave clean edges on thin materials (~15mils plastic sheets) and able to handle tight radius corner unlike cricut. 2) Can be scaled up to handle light metals as needed. I’m fine with putting some level learning/work into getting this running in the similar way the K40 lasers have a lot to get them going properly.

This seems to be a great current buyers for current machines that scale from low cost up.

I’m liking the cost, features of SainSmart Genmitsu 4030 PROVer XL. It appears this machine would handle the above described requirements?

In doing a bit more research it looks like I’d need to use a dragknife upgradable unit. Any suggestions on drag-knife upgrades to handle thin materials?

What are your thoughts on where to get started with good upgradability options?