32 spokes should be enough. I'd get a nice hand built wheel. I got rid of my Trek FX years ago because I was tired of the wheels & bike shop I bought it from with promises. Since I went hand built, I have never had a problem (3years). I'm a big guy and ride generally 100miles a week.

I'd imagine you could go lighter, but I've had great success with my Mavic CXP 33's (32spoke) on 105 hubs & 23mm tire.