Shimano

I have an old Bianchi with Shimano 105 parts - 9 gears
I would like to replace the crank with a compact (getting old ...)

any idea if the newer cranks (designed for 10 gears) will do the job?
how about the FSA components? do they work well with Shimano parts?

I'm not strong enough to push a big ring up proper hills, so I'd like to swap my dura ace chainset for an equivalent compact.

It's 7800, in very good nick - a few of the usual scuffs but nothing bad. Teeth look good too, hasn't done too many miles. Crank length is 172.5mm.

I'm looking for 7850, or similar - I'll consider SRAM, FSA etc . gotta be compact though.

Pictures here:
http://www.flickr.com/photos/bashthebox/sets/72157628816098477/

Any ideas on where I might be able to get a pair of these
from to fix up my winter bike, I guess it's that or a whole new drivetrain that I can't afford!
Current shifters are Shimano RSX but any considered!
email: andybnk@aol.co.uk
Thanks