For the Trek FX Series, the 7.4FX is the sweet spot for me. I really wouldn't want 28mm tires on my FX, anyways. Plus you're getting a nine speed and a CF fork! All of your components are fairly decent at that level. A Deore RD is just great! It's the same as what's on the 7.5FX.... Acera for a FD is just fine too! You're not really getting that much going from a 7.4FX to a 7.5FX...

* I'd try to avoid an alloy or aluminum fork, if I could opt for a CF fork.