If you guys want a twin turbo setup just go for it, by the time they figure out the bugs in their turbo kit, 2 years will have passed by. I doubt it will be smog legal when they figure out how to trick the ECU, but I could be wrong.

You need to find yourselves a good tuning garage, and have them do it for you, or else do it your self. It's alot of work and it will cost more than $2,500 to put it together for our cars.
1st, you need to fab up an intake, which will take a bit of time and engineering,
2nd, you have to fab up some exhaust headers, and blow off valve,
3rd, mount your turbos, in a safe place so there is no fire risk.
4th, mount you intercooler,
5th, connect all the plumbing,
6th, where are you installing the air flow meter? and will all the stock xf sensors operate under pressure correctly? more research time.
7th, might need a heavy-duty clutch to handle the power.
8th, either a stand alone ECU or piggy back computer
9th, getting it drivable, then dyno tuning.
10th, passing smog.
11th, reliability testing.
12th, pay your labor bills.

And then how long do you expect this set up to last, on a N/A block?
13th, new forged crank from SRT6
14th, SRT pistons and rods. and maybe srt cams?
15th, pay more bills
16th, now you need a higher flowing exhaust..
and the list grows longer...

before you guys know it you just dropped $15,000 - $20,000 on your twin turbo kit. this just doesn't seem practical to me.

IMOP, sell your Limited XF, take that money and put it down on the SRT6 and then start from there and see if you still feel like spending money for modifications. Sorry to be a buzz kill but I'm just looking at reality, and a $2,500 twin turbo kit sounds like a nice fantasy..

Otherwise spend your money on the Kleenman kit and have them do the work. they already did all the engineering why waste your time trying to figure it all out yourself?