Well have a 3040 and its been a learning experience, but one that has been worth the cost the learning.

To be fair they are marketed as engravers not billet aluminium mills ;-)

The wiring on them, maybe changed in last 3 years , was very brittle , went intermittent, rewire of motor cabling cured that.

The control box uses Toshiba integrated drives meant for photocopiers, they can be bit sensitive, but after a rewire and replacing 2 chips, fingers crossed , no further trouble.

The spindle ,on cheap 3040, was a reused servo motor core, it`s only 180w so cutting deep aint an option.

Item linked above has a big 800w water cooled spindle , less of an issue, control box looks very similar.

Unsupported rails on the long axis on one linked would limit accuracy in hard materials would guess, its horses for courses.

Consider a Chinese frame with better electrics fitted?

Also need to budget in for software, genuine Mach3 licence and CAD and CAM software of choice.

P.S. its the internet a bit of banter is what its all about , yesterdays news is todays chip wrapper ;-)