I wouldnt touch a cam until after you get the basics in there first.
I would go with 4.56 gears, headers and an intake before a cam. All of those will really wake that HEAVY truck of yours up. Gears figure $1000+, Headers $300-$700, CAI $50-$300, and there is your $2g's right there. Also that combo will help with your mpg's as well. IMO a cam in your truck, as it is now, would be a waste of money.
If you do decide to get a cam in it though, you need one that will run with the superchips tuner (so nothing "big") and you need one that puts out gobs of lowend tq since you have such a heavy truck. Also, bare minimum with any cam you look at, upgrade the springs and rods to the 6.1's (unless its a custom ground cam or regrind, then you may need a custom sized rods), most of the cams out there require at least that as they are based on the 6.1 cores.
For the record after everything was said and done, my cam ran a little over a grand to get all the parts and get it in and running.