I haven't actually tackled an e1e head yet, but it's on my to do list. In my experience though, modding KL4 with the reflector and 1W LEDs, I'd take a reflector over an optic any day. The only thing is the heat.
Are you talking about boring the E1e head to accept an optic? I'd go with the KL1 if you're gonna do that. It's a little bigger, but it handles the heat better. If you go with the reflector, which is what I'd do, stay conservative with the current. Like 400 or 500mA and it should be a very nice light. I've wanted a modded E1e head for awhile. I've seen the pics and they are impressive.