Supras aren't rare... I used to have a Civic Type R and I see at least double the amount of Supras on the road.
It's unfortunate but at the end of the day the rarity of the car shouldn't matter.
I would take the "Armytrix quality is bad" claims with a grain of salt. I saw that A90 shop posted about the bad quality on their website (which is very sus for a reseller to do that).
All the reviews on the forums from what I read are pretty much always good. If you want a catless downpipe...