Just thought I'd share my experiences:
I'm 6'3", and I drive a S14 with a sunroof. With the stock seats, I had plenty of head room, but my legs were kind of cramped (I'm on of those guys with really long legs). Then I swapped in a pair of Corbeau GT7s.
With the Corbeaus, I can't slide the seat all the way back or my legs won't reach the pedals (woohoo!<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt='
'>. Granted, the front seat does touch the backseat, but I was going to take it out anyway. My head does hit the roof now. If I tilt the seat back, I'm okay (we're talking .5" of room). But no helmets for me.
I've been toying with the idea of getting Bride rails, but I'm just not sure how much they will help. The thing is, my Corbeau rails mount the seat lower than the stock seat, BUT the GT7 is 2-3 times thicker than the stock one, so I sit much higher.
One thing about aftermarket seats, they're with you forever, and I say get as nice a set as you can afford. I've had mine for 4 years, and they've been in 3 different cars: a '67 camaro, a '86 VW GTI, and now my S14.
They're starting to look a little worn, so if I get them recovered, I might get some of the bottom foam cut to lower me an inch or so.
I don't know if all this rambling helps, but I thought I'd share anyways. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='
'>
-john