Getting my first CNC and I have a few questions. My budget is around $3500 with hard cap at $4000 for hardware.

1. After doing some research it seems like Onefinity seems the best build quality in that price range. see link below If you guys have other opinions I'd like to hear them and why it would be better the the 1F.

2. They sell a base/frame for the machine to attach a spoil board. The one I'm looking at particularly is has a 32 x 48 cut capacity and is $525. see link below. Is that expensive? Can I build my own from 8020 1530 extrusion for cheaper but have as good (if not better) quality? Or am I being cheap

3. For now I will probably just use the Makita trim router that the machine was designed for but in the future I want to upgrade to a spindle. Onefinity sells a 80mm mount. I was talking to someone who owns an axiom machine I believe and he said his machine comes with a spindle that uses hydraulic fluid as coolant and it's self contained. ie NO hoses. Do you know if I can buy that as an aftermarket part? Would it fit a 80mm mount? Any links to show examples? thanks