Go to the top of the page, click Resources, then click Multimedia Studio. You will find some exhasts on there. I would say the Nur Spec R is the most popular and is claimed to be the best performance exhaust available for the Supra. The HKS Hiper is another popular one that is a bit louder and produces more of a "burble" sound.
I have the Hiper myself and heard the Nur Spec. I wouldnt change it out for anything.
As for your questions of running higher boost, I wouldnt really worry about it unless you do the full de-cat. If youre trying to question the cost of a Boost Controller, I will say its a hell of a lot cheaper than replacing blown turbos! Especially if youre running J-Spec ceramic bladed ones. There are a lot of people that use restrictor rings and never had problems. This would be your cheapest route... again, if you go full de-cat.