Just to throw in my 2c - I've used someone elses SL140 with the RC150 and the suction cup roof mount thingo on a 93 landcruiser and the handle was way too short for what you want, it was painful after a while. I'm not sure which handle would work with the door mount though - does anyone know if its easy to shorten the handles? If it is maybe buy the longer one and shorten to taste. The gimbal mount is awesome, adjustable tension and the light definitely stays where you point it, but takes a little bit of effort to sweep the light (I'm sure the longer handle would have helped me with that setup). I didn't mess with tension on the one I was using, it was someone elses rig but I'm sure the sweet spot could be found.
I've used a HID converted handheld lightforce 240 very recently and I didn't think it was very good. I think it was an ebay kit fitted to an older housing. The light is lacking in wavelengths just like compact fluoro's in your house so you don't get the definition at distance like with a normal incandescent bulb. I didn't even think it was as bright as a normal 100W bulb, but it was a 35W kit not a 50W kit. I wouldn't waste the time or money on one now, be happy with a normal 100W bulb and run 6mm2 cable to the light and big crocodile clips straight to the battery. Oh and waiting for the HID lamp to warm up to full light after switching it back on takes far too long and it doesn't keep your hands warm like a normal light either