+1 on 997. The 996 looks fat, bulbous, and damn ugly at some angles. YES i know they follow the same formulas and similar curves and design etc etc (since all 911 looks the "same"), but the 997 is just much better not just in terms of looks both exterior and interior. Performance is a big step up. The AWD drivetrain is much better and much improved overall. Turbos are tweeked better and is more fuel economical. Boost comes on much smoother and linear and feels more refine (although this is barely noticable since both cars are actually pretty comfortable to live with) (and also might not be a good thing if you're looking for RAW Mechanical POWER). What makes the NSX so great is that it feels refined, great balance and suspension set up, but also it still seems raw and a true driver's car when you push it.
Lastly, if given the right budget, the GT3 might be a better option if you dont mind the lack or "luxury." Holds value just a tad bit better, crazy amount of fun, and a rev limit that will put a smile on anyone. That being said, knowing that Premium fuel here in BC is SUPER expensive (something like $1.65/L now? around $5.80 USD/Gallon) Then the GT3 might might not be as attractive. With so much revving fun the GT3 packs, i'm sure i'll see you very often at the GT3's natural feeding habitat - The Gas Station.
Regardless, Porsche is porsche. I prefer old porsches. But if i can choose a new'ish one, i'd go for 997 GT3 non RS. Just the good ol regular GT3 (will be more than enough for me). Also has to be the one with the center wheel lock, looks freaking fabulous.
Between the 996 turbo and 997, obviously, the 997 turbo wins in every category besides price. Good Luck and have fun!