Need advice on first build

Hello, I've been doing a lot of research on here trying to find what I want to do for my first build (outside of drop-ins) but I haven't been able to find something along the lines of what I have in mind. I see most people go for the XM-L and SST-90 for their lights, but don't see too many Luxeon Rebels. For some reason I find myself partial to those, so please let me know if I need to completely relook at my build. Are the rebels just simply not bright enough? I could see them being more difficult to utilize reflectors with. My goal is to have something really bright, but not necessarily a mega-thrower, and I want decent runtime.

I have a 3D Mag that I want to put 3 Tri-Star Rebels in. I would go with the 18 degree Carclo optics. Do I still need/want a reflector? I was planning on just not having it in there anymore. I like the open LED look where you can see the wires and such. These would give me a theoretical 2070 lumens driven at 700mA. For the driver I'm looking at the LuxDrive 2.1A BuckBlock. I would hook it up to have 3 parallel circuits of the 3 LEDs in series. I'm sure that's not the technical way of describing it, but hopefully you get my idea. Am I better off with a different driver? I know DX has a lot of cheaper ones that seem to have similar specs, but I'd like to spend a couple dollars more on a more solid product if it will indeed be a better product.

For the battery I was thinking 3x 18650s since I'm having a real hard time finding 32650 or 32600s. I was considering having the body bored out to accept two 18650s side by side to be able to run 6x 18650s for additional runtime. But that might be a bit much for my first build. As for heat dissipation, I was planning on taking an old CPU cooler and grinding it down with my bench grinder to make it fit into the head of the Mag, making sure that it sits in there comfortably to utilize the head for additional heat management. I haven't seen much on here about using arctic silver to mount the LEDs to the heat sinks, is that pretty much the standard? That's what I've always used in my computer builds and it seems to work fairly well.

I'm sure there is a lot I'm leaving out, as I said I'm still new to building flashlights. If somebody has already made these same mistakes I'd like to learn from you instead of wasting time, energy, and money on something that you guys would have told me wouldn't work out anyway! Thank you.

Is this site really that against the Luxeon brand that I don't even get a single reply?!?

The 2.1A Buckblock datasheet suggests that it is the wrong driver for the application. You have three triple Rebel stars, with the triple LEDs on each star wired in series. The three stars themselves are then wired in parallel. Thus, Vload is 3*Vf. At 2.1A total drive, each star will see 700mA (assuming that the stars are exactly the same) and each Rebel on each star will also see 700mA drive. Thus, Vf for one Rebel is about 3V, and thus Vload is about 9V. With 3xLi-ion powering the Buckblock (11.1V nominal), you don't have enough Vin to power the driver sufficiently. The datasheet says you need about 18V of input voltage to be able to run at 2.1A drive. Extrapolating Figure 6 of the Buckblock datasheet, it looks like you might get about 1.5A drive at 11.1V input, or about 500mA per Rebel. Of course, being an extrapolation, it could be way off depending on how those curves really fall off. It could very well be basically zero drive current, not 500mA.