Same dilemma here, @SVTFreak, except now most (if not all) of the GT350 HEP cars have been sold and are firmly in the "used" category which makes the decision even more difficult.
On the one hand, I can easily get want I paid for my 50th GT LE 5 years ago back in full because of the crazy used...
Yes, I installed the Ford Performance Power Pack 2 on my 50LE (WW, 6M) and have contemplated a catback exhaust system but haven't pulled the trigger on that yet. I went with the FPPP2 on my 50LE for many reasons, but partially the ones you and gearhead2685 are espousing in this thread.