I highly suggest you go out and sit in the seats you're interested in buying. I know that Sparco and Recaro both have varying sizes for their non-adjustable seats. Personally, I like the Recaro SRD.
The reason this sig pic doesn't work is because Bernie says I suck at inet. =) "Man, a car full of ugly girls in an explorer tried to chase me down today, I almost vomited then floored it and got the hell away."-nadir