I can get the large yellow top here at costco for about $170 so i'm not sure that's a very good deal?

I haven't looked at my engine bay to do the big three, i'll probably be undertaking that this weekend/next week if i can get access to some 1/0 locally. I use 1/0 because there's no reason not to. The wire is kind of expensive but so is filling up the gas tank.

your amp is not pulling full load all the time, so your alternator should be more than sufficient. I find it more than hard to believe that you need to upgrade your alt with what you're running. If that's truly the case, it's because there's something already wrong with your system.