Hovering over "Buy"... care to sanity check my thinking?!

[JAZZCNC]

Ah yes, sorry, you're right, I meant Mach4. Ok, that's cool then, I'll stay with the parallel port. Glad I kept that old IBM Thinkpad now :D

No wouldn't use parallel port either. I was saying Go with Ethernet over USB but if choice is between USB and Parallel port then USB every time. Also Don't use Laptop with parallel port and Mach3 they are too unreliable.

Digital drivers is a new one on me - guess some more reading to do - do they need different motors, presumably? No problem if it's a complex answer, I'll do some reading on the forum, just curious.

Digital drives are far superior in performance and reliabilty to Old Analog technology because of the advanced way they handle resonance and current/voltage etc. The difference is quite large and has to be experienced to appreciate the true difference.
They work just same regards motors you can use.

I guess any upgrades to the electronics can be considered an investment, assuming the drivers and motors remain matched..... maybe I can keep the motors and spindle, if nothing else, if/when I do make my own.

Not really because any machine is only good as it's weakist link and there's too many weak links. Also if idea is to re-use on another machine then this needs careful consideration because how do you know what you'll need without having the machine design.?

Am I right in thinking the main thing I need that's really lacking is the rigidity in the gantry, the quality of the runners, lack of support on the Y and just general strength/"trueness" in the aluminium extrusion approach...

It's multitude of things really which all bring it down. The actual strength isn't too bad it's the low quality of rails and bearings etc that let it down.

Here's the crux question then - for the PCB work and aluminium work (slow, hobby, prototyping stuff, low volume, 0.1" through-hole and SMD designs) is the extra £400 on a 6040 worth it over the 3020? The only real differences I can make out are the crappier spindle, the crappier ball screws and the smaller working size. The latter I couldn't care about :)

Forget aluminium it will destroy the machine in no time. The rest it will do. Thou I would say stay away from the Cheap DC spindle and Lead screw versions. All have rubbish electronics so that's just a lottery.