Wow that was a lot of reading I just did! Haha, but anyways it seems like you know what you want, a very fast and reliable supra! So if you were to upgrade a 7mgte here is a basic outline of stages to do
http://www.suprastore.com/stivimk3tu7m.html
This is what I'm trying to follow right now, but keep in mind that you should always have extra cash for there are always maintenance issues that may come along with this car and any other turbo cars you plan on modding.
Something you can try also is to swap to a 1jz engine for it is known to be more reliable than the 7mgte (because of the 7mgte's BHG phenomenon) but yeah, and the 1jz twin turbo puts out around 280hp vs the 7mgte's 230. And then a lot of people would swap the 1jz's twins into a single turbo, and of course the bigger the turbo, the more power! Anyways I hope this helps you out it anyway!