For most people 64 bit doesn't offer a lot of performance gain... it helps out the standard user a LOT in compression and extraction of like zip and rar files... but obviously if that's all youre getting from it... not really worth it.
Now since you mentioned photoshop and 3dsmax those are both applications that have shown anywhere from 30-40% increase in performance at times when using the 64 bit binary versions instead of the 32 bit compiled versions. I would say for your uses it DOES make since to go 64 bit Vista. Unfortunately that leaves you with only one option.. the 64 bit Ultimate version as that's the only one I'm aware of that they have a 64 bit version of. Good thing it's the most expensive :)
Steven