I bought a 2005 Trek 520 late last fall and I weigh 235 lbs. The bike came with 700X32 Bontrager Race Lite Hardcase tires and generic spokes which were fine for ripping around the bike paths but for loaded touring I found 300 lbs to be too much for the wheel sets and I broke spokes 2 times and had to have the wheels trued twice in a month.
I had a set of wheels with LX hubs, DT double butted spokes, Mavic T520 rims and Schwalbe 700X35 marathon plus tires on them on my Fisher and I mounted them on the Trek. Made a big difference to me.
The ride of the 520 frame is great when loaded.
Jim