I came very close to putting Banks on my truck until somebody here showed me the dollars and cents of the thing. Using other suppliers he was able to give me everything I was going to get at Banks plus a turbo for the same price as Banks without the turbo.
For myself, I was impressed with the land speed records that the Banks team had set. But don't be under any illusions that Gale Banks is going to take a personal interest in your truck and that you will be getting the same equipment that went into that truck. You'll do far better finding a good installer in your area that knows his stuff and can give you good advice.
Around here, the hot mods seem to be:
electronic boxes: Smarty+TST+MP-8 (max power & max smoke)
Edge Hot Juice & EZ (more civilized, but a little less power)
Gauges: You need EGT & Boost. These are included in the TST box or in the Edge Juice w/Attitude. If you start with just a programmer such as the Smarty, you will need to budget for the gauges. If you like gauges, you may want to include a gauge for fuel pressure and rail fuel pressure as well.
Air Intake: AFe or BHAF, depending on your budget. If I was doing it over I would go AFe. It's on all the high HP trucks around here.
Air Intake Horn: The Banks one has been dynoed as a power robber, and you really don't need it, but if you feel the urge, check out the new Glacier Diesel Power design in the R&D forum. It hasn't been dynoed yet, but the design is at least sensible. The CFMplus is pricier, but has been flowed head to head against the Banks unit, and substantially outperformed it.
exhaust: MBRP is popular, I went with Rokktech due to the reduced noise. Your piping is 4", so all you really need to do is replace the muffler. I don't think the specific model of performance muffler matters much -- it's really a matter of taste when it comes to the sound.
Intercooler: This is not a particularly popular mod because it's not cost effective unless you are really worried about EGT's, but since Banks offers one I will tell you that I love my Spearco, and that it outperforms the Banks unit.
Turbo: size it for your application. For street use, the HTT Super Stock 62 is a good choice, and the Industrial Injection Super Phat Shaft is a popular alternative. This will do much more for you than the Banks intercooler and 4" exhaust piping that replaces your existing 4" exhaust piping, and the Banks High-Ram intake that robs you of 12 HP.
Fuel Pump: Glacier Diesel Power (which I strongly prefer) or FASS/Airdog. Not strictly sure these are necessary, but they are popular. If you get one, make sure you get a 2 micron or better fuel filter. The stock fuel injectors and fuel filtration system are one of the weak spots on the vehicle, and if you are going to overfuel the engine you want the fuel as clean as possible.
Transmission: You really need to do something to upgrade it if you are going to be adding more than 100HP and especially if you are towing. Suncoast & Goerends are popular. ATS is also worthy of your consideration. If you've got a manual, I think South Bend clutches are popular. On the other hand, you can just drive it till you blow it out and get a new one then.
That should get you started spending money on your truck. After those upgrades, you can think about injectors, camshafts, dual CP3 pumps, porting the head, nitrous, and water/methane injection.