Not to pollute your thread (since it wasn't on your radar to begin with)... but unless you're running a full time business... I doubt the "continuos use" would be an issue. As for versatility... I'd be curious what you're seeing the T-4 wouldn't do, that you need?
As for your other choices... I think part of the answer of "which one"... depends on your goal(s). You mentioned you've been sharpening "so many knives"... are you looking at a business setup? Volume might eliminate the KME for example. Also look at other things like, what if something breaks (down time), replacement parts, customer service, etc. And, what type of knives do you mostly think you'll sharpen? All are decent sharpeners... so you might look at "external factors" to help make a decision... and be bit more specific on what your goals are.
OTOH, if you're mostly still sharpening as a hobby, and/or like trying different setups (like I do), you might consider dividing your bonus between a couple of your considerations. Might be more enjoyable in the long run.
Just a couple of thoughts!