My turn, my turn... . lol. Welcome to the Forums bud.
I dont have the auto, but I have the Quadzilla Adrenaline, and this thing ROCKS. If you were to invest in this item, you might want to upgrade your transmission/TC. Alot of the guys like the Smarty. Some even look into custom live tuning. If money is tight, the Smarty or the Adrenaline is the way to go. On the subject of the adrenaline, you will get +180 gains in HP.
On the subject of gauges, yes. This should be the first thing that you invest in. Geno's is probably a good place to start. If not, check out farmboysdiesel.com ... Gus Farmer is very customer orientated. Also has great prices on the other goodies you were wondering about. But I digress, YOU NEED those gauges. I am personally running ISSPRO and love them... . its your call.
As Mr. Barlow had said, realize that these CTD are low RPM engines. The key here is to let the beast BREATHE. I would go this route as my bottom line. If money is tight, start with a guage cluster. Then I would move on to a better air filter, perhaps a BHAF. If more money is available, the programmer/chip/computer upgrade; however, realize that with the latter, you will need to trick out [a little] the transmission. If not, you will face some bad demons. Follow that [if cash is still present] with a exhaust upgrade. On a side note, if the money is available after budgeting this all, before you do anything, it might be smart (as I do) to dyno the truck before you stick anything on the rig... .
BEST WISHES DUDE!!!!!!! AND CONGRATS ON THE RIG
Kind Regards,
John