Recomendation on batteries?

[HUMMERcustoms.com/TAZ]

With the PC and some other electronics We plan to have surge protector and a way to stabilize the voltage. They will all be 12V so no converter needed. I'm still just concerned a little about voltage fluctuation just as You see the charge needle move with engine RPM's.
Does the battery itself tend to stabilise the voltage that is used by the electronics even the factory stuff?
I appreciate everyone getting in here and helping Me. Please continue to add info as You think of it or PM Me if You like. But, here it is at least recorded for future reference by others so get Me the info anyway You choose.
Any info to help in making the power use safer for the equip. is greatly appreciated. Please anyone get in here and help Me. I just worry about blowing something up that We have put allot of work in. The young man that is helping Me is truly a audio/video genius but, We have been building equipment and not discussed the voltage stabilazation yet. As We are approaching the home stretch it is something that I just began to consider today and always the forum gets ramped up quick to help. The info You are giving is making me more comfortable with the unknown as far as I'm concerned.
I did not relise it but the 34/78 is a red top and the D34/78 is yellow top so I'm thinking the yellow is what We were looking at. They do not have the CCA that the 31T or A has and that it what I was wondering if that could be a problem.
I talked to the Young guy and He said He thinks We may be able to fit 2 31T or A what ever the difference is maybe someone knows. so We will look at that i guess.
I would never have guessed that it could be so many choices as to batteries for particular purposes. I'm glad I got people I can ask this kind of stuff bugs Me.
Thanks
TAZ