After market seat recommendations

I'm looking for something that holds me snug for autocross and track
day, and won't kill my back on the street(I'm OK with using a pillow
for street driving to improve comfort). I've read the reviews at
Miata.net and the web, but I'm a bit worry about fit. I have to drive
a bit to visit any shops with racing seats for the Miata, so instead
of visiting all of them, I'm hoping you guys can help me limit my
search to particular brands or models. I'm 5'6, 145lbs, with a 34"
waist.

Also, I'm not worry about if the seat has a 5 or 6 point harness
holes. If the seat fits well, I'll get whatever harness works best
for that seat.

Thanks