what budget to you have ?
Is it a daily driver or weekend toy?
Which 911 poster did you have on your bedroom wall as a kid ?
If you want the 911 experience & have dreamt of them since a kid, go for the aircooled cars .... IMHO, don't bother with a 996. Still depreciating, potentially expensive to maintain ( RMS issues & more electronics than earlier cars ) , but more importantly a more diluted driving experience.
If you are on a lower budget ( less than £15K) do look at 964's & 3.2's.