I have the Trek 7.3 fx and have about 600 miles on my bike with no real wheel issues at all. I think I have a bent or worn tooth on my crank somewhere though. Granted I am not as heavy as the OP but still about 290lbs for most of those miles. I am usually pretty good about trying to miss potholes and such but do hit the occasional pot hole pretty hard and have even jumped a curb or two where my bike path crosses a road... why there are no ramps I don't know but at any rate the wheels have held up under my weight and abuse.
As for the OPs original question I love my FX its been a great bike and plan on putting a lot more miles on it this year. The only problem I have had is the one I mentioned above. I did have the chain replaced and new brake pads put on back in Feb. I only have that problem when I am really putting some force down on the pedals usually going uphill... I have to take the bike back and have them take a look at it just to be on the safe side. All in all a great bike though.
As for the wheel issue I don't know what to tell you. If you have the money and don't mind dropping another $300 go for it. Its not going to hurt anything other than your wallet.