I think the XML LED units are a lot of light for not a lot of money, but the lamp/reflector design has a lot to do with the overall output - as they can have a very 'spotty' beam (very little spread, not the best). Either way this 'late' in the season I'd suggest you 'try' a single unit for your head, unless your planning some late late nights, early morning usage (or 12 hr races). One unit will be enough to get you started and you can decide if you want a 'better' or extra light for your bars before next autumn.
There are lots of better units out there, over a single XML LED lamp, but seemingly the normally very competitively priced MJ-872 has gone mad, as there no way I'd spend £125 on one, as per ebay pricing (check out the fluxient 4xR5 clones). Inton used to sell a MJ-880 replica, which my friend has & is the most awesome light I've ever seen (output wise) though is too heavy for anything other than bar useable
Little lost on what the difference between the C&B 1000/1200 unit are, other than the price (and CBA to investigate) as they use exactly the same LED (not to say it's impossible to achieve).