So I have been upgrading my trek 4300 slowly and have replaced the shifter, R/D, chain and cassette with XT, added new XC bars and stem, and Avid 3 brakes. Looking to upgrade the wheel sets, cranks w BB and fork. Just wanted to know what ya'll think would be the best choice to upgrade first. This is what I have currently on the bike:
Wheel sets, Shimano M475 hubs with Bontrager Ranger rims 14g stainless steel spokes 36 Hole.
Crank set, Shimano M311 22/32/42 w/non-changeable chain rings, and a square taper BB
Fork, OEM Spinner 300 hyd w/ lock out.

The type of riding I do is mostly single track XC with some good amount of rock gardens to ride through and over.
Thanks in advance for the help and advise.