Since you've decided to install 800 W, the Tristar 45 MPPT is a good choice. If you were targeting 400 W I'd suggest you look at BlueSky's 3024 MPPT since you can add an optional remote to obtain battery monitoring capabilities. Whatever solution you choose, I highly recommend that you install a battery monitor so you aways know how much battery capacity you have consumed.
Assuming you continue with the 800 W, you have two choices: create four groups with each group consisting of two panels in series, or create two groups with each group consisting of four panels in series. The former configuration will need to pass 5.29 A * 4 = 21.2 A, while the latter configuration will need to pass 5.29 A * 2 = 10.6 A. You cannot put all eight panels in parallel with this controller.
As Lew said, you do not have any systems on-board that can benefit from creating a 24 V or higher battery bank. Stick to 12 V so that all your systems will be compatible.
Typically your solar controller is wired directly to the battery bank. This way the system can always charge your batteries.
2015 30' Classic, "Chez Nu"
2014 RAM 2500 w/Cummins Diesel
ProPride Hitch, 400 W Solar