^Well I can put in my .02 unfortunatly... I bought a set of the fake brides (brix II) from a friend who was too big for them. they were brand new, unused. Granted, it is not a fixed back seat but it felt great, looked perfect, and worked great until...
I was drifting at the naples track, just me and josh. Going around a corner in mid-drift when all of a sudden I am looking at the roof and sitting in the back seat. The entire back rest BROKE OFF

. I had to wedge a bunch of shit behind it just to sit me up to get home and it was not very comfortable and really not safe. And i missed out on hours of free drifting, and this was on the COMPLETE (pre destruction) track
When I got home I puled all the cloth and padding off to revel the frame. To my surprise, it looked like it was tacked together with JB weld. And I even doubt the welds were as good as JB weld. That is the difference. I looks and feels exactly the same as the original but TRUST me they are not. If I would have been rear ended with that seat in my car I would have had my back broken at best.
Again, my experience was not with a fixed back seat but trust me. There is a reason Sparco, Bride, etc sells fixed back seats for $500 and up. I now run my stock seat until I can afford a proper fixed back. I hope your seats are better but do not be surprised when you find yourself wishing you would have bought one "proper" seat instead of two ebay specials...