Sell the 996, get the 997, with the X-51 you may decide you don't want the extra hp at the end of the day (who am I kidding?). From what I've read, and heard, the 997 C4S is quite an improvement over the 996 iteration. You could always sell/trade your 997 for the TT once it comes in, and in the meantime, you'll be having a BLAST in your X-51 equipped C4S!

BTW, I LOVE your spec. Have you thought about throwing the PCCBs on there (is it too late?)? That would really be spectacular.

PS: Let us know what you decide. I wouldn't mind taking your 996 off your hands if the timing is right (for me). And then take the 997 off your hands when you pick up the TT. I guess my advice is biased towards my needs, oops.

Since your in Nor Cal, be careful of the flood warnings just issued (even in SF!!!) Stay dry!