get a surly cross check and build it up like this...
hubs - phil wood or deore 36 hole
spokes - DT swiss
rims - velocity dyad
bottom bracket - phil wood or shimano sealed cartridge
cranks - any mountain bike cranks
derailleurs - deore LX
seatpost - thomson
stem - thomson mountain stem
bars - any mountain RISER bars (will be way more comfortable than drops)
headset - chris king
levers/shifters - anything mountain compatable
pedals - mks touring pedals, mks clips/straps
tires - big! 38c?
brakes - your choice
saddle - your choice
all of these components are the highest standard known for high performance and durability. if you go with this build you will be more than satisfied. also many can be found used on ebay. good luck!
and heres a surly cross check that was built similar to what i just reccomended...
http://www.andrewduvall.org/images/utilitybike02.jpg