I agree with sgtstix, but I'd also recommend the TVR Tamora, the Griffith's successor. If you don't feel like waiting for a Griff to show up in the used car lot in a color you don't like, the Tamora might be the way to go. Like the Griffith, the Tamora is very light and quite powerful.
If you don't mind a little more weight or don't want a convertible(Griff and Tamora are droptops), go for a TVR T350C. Only a little more weight, and just about as capable.