mini_mull
1/2 ton status
Chris, thanks for the props.
Now onto your questions.
As for SSA, I rate their products very highly. Everything I have used is as advertised and does exactly what they claim. The only reason I did the roof first was that I had to replace my headliner anyway and because as you guessed I wanted some extra insulation to protect me from the AZ sun. I think treating the roof did make a slight improvement in heat and sound dampening. Obviously the greatest improvement for sound would be from the firewall, doors, and floor. My plan for the floor is to first hit it with some rust bullet for insurance (spectrum is a waterbased product filled with rust inhibitors), followed by Damp Pro, and then spectrum or spectrum firewall 3-4mm thick. After that I'll either follow with herc or replacement rubber mat. If you plan on doing herculiner and want to be able to hear anything in your truck besides road and engine noise I would suggest using spectrum under the herc or using sprectrum as an undercoating. Herculiner has almost no sound dampening effect, so if you take out all your carpet and mat that's about what your truck will sound like after only herc. Oh, and painting the roof just might help a little, I have thought about it (great minds think alike
), esp in between the ridges on the roof, I'll probably try it out before I get a new paint job.
As for the battery, for your diesel, you need it wired in parallel to get started, but for us gassers wiring in parallel gives us the least amount of options and protection. When you wire in parallel you are essential making one big battery. You can't jump start yourself, charge one battery at a time, or keep from draining both batteries at the same time. Most people install a second battery as insurance for jump starts and to help run things with high draw like winches, elec fans, welders, stereos. Running batteries in parrallel won't accomplish any of these things, you'll just turn over the engine easier. There are many different systems out there that use isolators, solenoids, or ACRs to get similar results, but each had it's pros and cons. If you search for the dual battery thread, esp the ones that ryoken has contributed to you'll find a lot of valuable info. Being a diesel, you can add a third and even fourth battery! Or maybe just two higher rated batteries
, ryoken would know. 
I'll be watching for you to start your build. Let me know if I can help with any more info.
Now onto your questions.As for SSA, I rate their products very highly. Everything I have used is as advertised and does exactly what they claim. The only reason I did the roof first was that I had to replace my headliner anyway and because as you guessed I wanted some extra insulation to protect me from the AZ sun. I think treating the roof did make a slight improvement in heat and sound dampening. Obviously the greatest improvement for sound would be from the firewall, doors, and floor. My plan for the floor is to first hit it with some rust bullet for insurance (spectrum is a waterbased product filled with rust inhibitors), followed by Damp Pro, and then spectrum or spectrum firewall 3-4mm thick. After that I'll either follow with herc or replacement rubber mat. If you plan on doing herculiner and want to be able to hear anything in your truck besides road and engine noise I would suggest using spectrum under the herc or using sprectrum as an undercoating. Herculiner has almost no sound dampening effect, so if you take out all your carpet and mat that's about what your truck will sound like after only herc. Oh, and painting the roof just might help a little, I have thought about it (great minds think alike
), esp in between the ridges on the roof, I'll probably try it out before I get a new paint job.As for the battery, for your diesel, you need it wired in parallel to get started, but for us gassers wiring in parallel gives us the least amount of options and protection. When you wire in parallel you are essential making one big battery. You can't jump start yourself, charge one battery at a time, or keep from draining both batteries at the same time. Most people install a second battery as insurance for jump starts and to help run things with high draw like winches, elec fans, welders, stereos. Running batteries in parrallel won't accomplish any of these things, you'll just turn over the engine easier. There are many different systems out there that use isolators, solenoids, or ACRs to get similar results, but each had it's pros and cons. If you search for the dual battery thread, esp the ones that ryoken has contributed to you'll find a lot of valuable info. Being a diesel, you can add a third and even fourth battery! Or maybe just two higher rated batteries
, ryoken would know. 
I'll be watching for you to start your build. Let me know if I can help with any more info.

As for being worth it, I don't know really. If you value every degree then yes, but it is a lot to spend for results that don't cure the problem. I'd have to move somewhere cooler to solve the problem. 