Hi WW2 - 1) You can build cheaper control systems if you shop hard for all the parts and hone down the specs to the minimum. Then you have to put a lot of time into assembling them, checking them twice and making sure you don't let any smoke out. If you let smoke out then you have done the budget and it becomes costly. It's easy to make smoke with these things!! 2) by getting an all in one solution the chances of letting the smoke out is small. You save time in wiring and getting the right wires and you use much less space in the build. I have a gecko 540 and it's done very well. I have abused it and it has survived. I have also built component level systems (let the smoke out twice) takes a long time to sort.
So if you don't have time or are not electronics savvy get the all in one solution. If you have a week or three to figure out all the connections and you like doing that, then get separate components. I've done both and to my mind I'd go with the one box approach. But the G540 is limited to 3,5A and this means you can't put big motors on it. Not even large N23 or N24's. And I think they say if you run 4 motors then its 3A max on each? I'd look at Buildbotics 6A per axis and many bells and whistles (this covers all N23 and N24's and some N34's). Comes with the wires and external controller. A good thing. I'm planning my next build B#4 (I've built 3 machines so far) and that's what I'm going to use. Peter
https://buildbotics.com $450USD plus need to buy a power source, I think this is well ahead of the other solutions.
G540 pluses - it works very well, technical support very good
G540 minuses - soldering the small connections is a pain, you will have to use limiting resistors as your motors are at full axis capacity and may trip the system like mine did initially.
Buildbotics get so many more features than above, more capacity, S curve motion, hand controller, don't need a dedicated computer for the machine, Plus plus plus....