Mike Focke brings up a very good point....
The OP has already lost $36,000 since 2007 (car cost $66k, expected trade $30k) and in 3 years time he will lose another bundle (say another $25k when / if he trades up to the 2014 model. Thats a lot of money to give away...
On the other hand, his existing 2007 S fitted with a Raby 3.6 litre engine complete with all the upgrades for around $16/18k and the Flat6 warranty would still look attractive $$ wise.
And it would fly too - over 300 hp would make my smile even wider. I think every time I opened the taps, I would forget the upgrade costs....