Afraid in my opinion, and it is only my opinion
. but Geckos with DC servos would be a downgrade as far as I am concerned. I am not saying anything bad about the Geckos or DC servos, they are great especially at the price they are. You however have much better motors already and the cost of getting suitable drives will probably work out less than getting new motors and Geckos. In addition to that the configurability and features of your drives will be much much more than the Geckos.
Swapping out motors will also probably mean motor mounts, different pulleys etc etc. so a lot more work.
You can also do what I am doing as far as future proofing is concerned, keep your eye out on eBay and pick up spare drives and motors etc when they are cheap. If you are desperate for drives the only ones on eBay are expensive, when you dont need them then the cheap ones appear, think its called Sods Law
Hood