What's the beefiest front shock (26"), avail in quick release, with travel of 100-125mm (no more)? Details:  I mostly enjoy XC and all mountain riding. However, I also from time to time, will go out with friends on some much more intense downhill trails.   I'm also about 240 pounds, give or take.    So, while I really really like my bike, and the geometry is fine (as far as I'm concerned) even for some downhill.   The fork I'm running now is an older Fox 125 RL. But, being 245# and bombing downhill really makes me nervous.  Since my bike is pretty high-end (titanium fame, King/Thomson/Race Face.....etc), I'd like to just (if possible....and maybe it isn't) add a really, really solid fork up front.  Weight it not an issue (for obvious reasons).  Geometry obviously is, as the bike is designed for 80-100 travel up front.  I go 125....but that's it.   Is there such a thing as a fork with 36mm or larger uppers with only 125mm or less travel??     

Hope I can turn this xc bike into one that can handle anything thrown at it with my 245# riding.   ??
You could look into dirt jump forks, such as the Marzocchi Dirt Jump or the RockShox Argyle.  There aren't too many options left for burly forks with 9mm quick release drop-outs.

Honestly though, Fox makes some nice forks.  Email their support and describe your use case (avoiding terms like 'hucking' or '6 foot drop to flat' unless applicable).  

I would be more worried about an XC frame and wheelset failing than a modern suspension fork from a reputable brand.