I don't know how much current the kl1 feeds the old lowdome but you can be relatively certain that it isn't enough to maintain the "XO" of the UXOJ. The beam will have much more tint underdriven.
I'm assuming the sxoh is a lux1 , and it should produce just as much light , if not more of a better tint and perhaps even better runtime.
SX0H will be cheaper and have a perfect tint when driven at KL1 levels.
I'm curious how well the optic of the old one can handle the high dome emitter versus the stock low dome. While you're in there maybe you could put a reflector in?