I've been looking as well and have heard a lot of good things about the ARC Performance DT-S Catback. It is valved, has a nice deep loud tone that isn't raspy with no drone.
So I just purchased a set of matte black MRR FS06 wheels. I was reassured by the rep at Audio City that MRR knows the proper flush fitment for a Supra, as they've had a couple Supra "sponsored" cars with this exact wheel. As you can see from the pics there are two major issues. The front wheel...
Love your entire build! Are those wheels Rays Gram Lights? I'm upgrading wheels now and love that look. Also going with 305 on rear. Can you tell me your wheel width and offset?