First of all, Welcome to the group!! Glad to have you join us. IMO, forget the exhaust for now and revisit that when you have a little more to spend. $800.00 will buy you a good CAI (AFE, Airhammer, K&N, Mopar, etc.) and the Diablosport Predator tuner. These two combined will open up your 5.7 in ways that will probably surprise you. The exhaust will help, and will be a little more expensive. As far as the tstat, it is just a function of keeping the engine running as cool as possible, not a problem with the OEM tstat. Once again, this is also where the Diablosport comes in as the 180 tstat in itself does not do much unless you reprogram your cooling fans - which is done with the Predator. I am sure others will give you their feedback and good luck in your decision!! Please let us know what you end up doing and how it feels.
Keith