VAC floor/side mounts, sliders, and lap belt adaptors will cost about $700 alone. Figure about $200 for shipping the VAC stuff and the seats. Which really limits your choices.
I am 5'10", 170 lbs and I have fixed back Sabelt steel tube seats in my E46. They are pretty roomy but snug. Definitely needs some more bottom padding for longer trips but that's a relatively easy fix. The steel tube seats are not really that much heavier than recaro's and cost $310 ea. The extra $400 for the Recaro's wasn't worth the 5lbs in my mind.
I had some REALLY good Recaro Profi SPG replica's for a month to see what race seats are like to DD. They were cool and felt good but it was way too tight for any long trip comfort. The sides squeeze your legs together which forbids any significant ball scratching or undie adjustments. You have to pull over if you've got some hungry butt that you need to fix.
Those are my observations from my shopping and research.
You feel EVERYTHING. The wallet in your back pocket? You'll feel that. One time, I got in the seat with my keys in my pocket...I felt that. Even drew blood as it force the key right into my thigh.
Cobra and Sparco are about the same as far as a snug fit. Corbeau seats are 100% garbage. The Sabelts are a good in between and provide a decent level of comfort.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red