There are times when I find that so-called white light LED flashlights are just not as good illuminators as incandescent flashlights. When light quantity and beam intensity are not as important as light quality - especially when you're interested in the light being returned from an object, at distance, outdoors.
So what I'm saying is that if you can appreciate your 6P's beam over an LED beam then a three-SF123A model will give you more light coverage (rather than more intense light). If this appeals then your choice is 9P, G3 or C3.
I prefer the Nitrolon over Aluminium so I'd rule-out the 9P in favour of the G3.
However, the C3 has a pocket clip so if this is important then it trumps the G3.
As mentioned, if you get a Fenix you get the 'current highest output LED' - a fashion item IMHO (nothing necessarily wrong with being fashionable of course).
As also mentioned, if you get a SureFire you are in many ways getting a 'host' for a variety of options - not just those options available now but those that
will be available in the future
If I was thinking about the future I would likely get a C2 rather than a C3 (in my mind a three-SF123A SureFire is for those who are active users of light for their job).
If I had only a 6P and was considering getting a more powerful incandescent I would seek out a SureFire dealer I can visit and see/handle the products for myself before making a decision.