Interesting comments. Sounds like you want the luxury of a daily driver / touring car that can also be competitive. This makes sense. My SRT is not my daily driver - I prefer two wheels for that. Nothing like ripping a wheelie on my 650cc torque machine on the way home for lunch.

Having owned both I can say the SRT brakes are all you should ever need on the road. I tested mine and came to a full stop from 140 MPH in ZIP. I also feel that the stock brakes on my limited were pretty dang good to. Competition racing might be another thing.

The suspension and steering on my SRT is far superior to my Limited. At high speeds, the rear end of my Limited wobbled like a fat ladies butt trying to rushing to the ice cream store before closing. The limited's touring suspension was good for just that, touring IMHO. Great comfort/ride on the road. My SRT is a bit stiff under 70MPH but once you hit 95+ it's a whole another ride to be appreciated.

The transmission is the one thing I am not sure about. I would assume they both are equipped with the same AutoStick, but my SRT tranny is much more tuned and well behaved. Off the line it knows what to do and does it without effort or question. My limited would freak out off the line and not give smooth shift transitions. When I was just cruzing, it was smooth and fine. Perhaps it's the computer parameters that makes the different between the two.

Anyway, other then HDDP whose advice has helped me out, you are the most aggressive Limited owner I have seen on this forum in terms of performance modifications. I hope you go the V8 route and if you do, I'm sure you'll be blazing a path for other power hungry XF owners.