WOW lad slow down on the buying blind or you'll end up wasting a lot of money.

First there are better options than Gecko and Smooth stepper/PMDX. From this I take you've been reading on our american cousins sites which are obviously Gecko and SS biased. Now nothing wrong with any of these products and all work very well but times have a changed and there are cheaper and better options.

But that said you are probably jumping the Gun anyway by presuming the drives need changing or any of the internals. Now I don't know the VMC190 at all but First you need to detemine exactly what motors and electronics you have on the machine. After this it can be decided what needs ripping out and what can stay.?

Regards motors and amps etc you Can't presume anything. The motors have a rating and for correct operation they need to run at this rating so it's not just a case of getting drives with a higher rating than the motors. The drive should have current setting that equals the motor rating or very close other wise you'll have either under performing or over heating motors. Some drives only offer fixed current settings Ie: 1A, 1.5, 2.1, 2.8, 3.1, 3.5 etc in which case you'd select the nearest lowest to avoid motor heating but this is 2.1a and your motors rated amps for best performance is 2.5a so your not getting the best you could from motors.
Now to be honest this is more a problem with cheaper drives anolog drives so if you buy modern Digital drives which I highly recommend you do if end up needing to then this probably won't be a problem because often they can be configured in software in 0.1a increments so can get exact current rating needed.

I' won't go any further as it will only confuse for now but If you can get us some info or very good quality pictures then can better guide you on what to keep or throw.