I'm not picking sides, just a FYI.
Is it truly an AMG vehicle? I don't know and don't care.
SRT . . . AMG . . . matters not to me.

But for the record:

From Car and Driver:
Chrysler Crossfire SRT-6 - Road Test - Auto Reviews - Car and Driver

Meanwhile, the dandy-dressed Crossfire, which shares both skeleton and muscle with the first-generation Mercedes-Benz SLK roadster, is the first Chrysler product to attain the performance-enhancing SRT label, heretofore bestowed only on Dodges.

Shorn of its decorative plastic sombrero, this Mercedes engine would look more familiar. It rolls out of the AMG handicraft shop in Affalterbach, Germany, and previously found work in the SLK32 AMG and C32 AMG. . . . . So the Crossfire SRT-6 is the last customer of a very nice hand-me-down.

Not just engine, transmission, and chassis:
There's been considerable pumping up of the Crossfire's suspension as well. The spring rates have been stiffened almost 50 percent in the front and 42 percent in the rear, and jounce and rebound rates in the shocks have been firmed up to match. The front brake rotors grow 1.2 inches to 13.0, and the rear discs go vented and get another 0.9 inch of diameter.

I always liked Csaba's quote too:
Cult-car alert! Twenty years from now, the SRT-6 will be one of those scarce machines that will command a prominent location at concours across the country. Just consider its exotic concept-car-derived styling, its Mercedes-based mechanical bones, and its outstanding acceleration, handling, and braking.

Another C&D article:
2005 Chevy Corvette vs. Chrysler Crossfire, M-B SLK350, Porsche Boxster - Comparison Tests

The Chrysler Crossfire SRT-6 is a brand-new model constructed on the foundation of the old Mercedes-Benz SLK32 AMG.

Assembled by Karmann in Osnabrück, Germany, the base 215-hp Chrysler Crossfire blazes with flair but dribbles with performance, which is most likely one reason the company has a nine-month stockpile of unsold cars. Peel back the molten-lead skin of our $49,995 Chrysler Crossfire SRT-6, and you'll find a huffy 3.2-liter supercharged V-6 from the AMG goody bag.

Motor Trend:
2005 Chrysler Crossfire SRT-6 - Exclusive Road Test Review - Motor Trend

The recipe for a good time on California's outrageously scenic Highway 1 is straightforward:

• Begin with one mega stylish, close-coupled sporty coupe. Whack off the top.• Amp up the engine compartment with a Mercedes-Benz sourced, handbuilt, 330-horse supercharged V-6.• Add a stiffer suspension, aggressive rolling stock, mondo brakes, and a functional rear wing.

Like all Crossfires, the SRT-6 is an international blending of pieces and teamwork: the powertrain comes from Mercedes AMG, the car is assembled by Karmann in Germany, and the design and tuning is done here in America.

The 3.2-liter helical-supercharged, intercooled, aluminum SOHC V-6 used in both Crossfire SRT-6s last saw duty in the 2002-04 Mercedes-Benz C32 and SLK32 AMG

Springs, shocks, bushings, anti-rollbars, wheels, and tires are all spec'd for higher performance, although there's surprisingly little ride penalty when compared to the base Crossfire. The SRT-6 roadster weighs about 90 pounds more than an SRT-6 coupe. Thus, it gets slightly softer shock damping, and lighter springs up front and heavier springs out back to balance out a minor shift in front/rear weight bias.

2005 Chrysler Crossfire SRT - First Drive & Road Test Review - Motor Trend

and now an amped-up version of the Crossfire called SRT-6, which employs the supercharged V-6 out of the old SLK32 AMG.

The result, assembled in Germany by Karmann, is an impressive performer. With a sub-five-second 0-to-60 run, near 0.9 g on the skidpad, and a slalom time that matches Evos' and Ferraris', the SRT-6 is serious stuff. We're placing our order for quicker and firmer steering, but it never feels disconnected, either. The front end turns in nicely, morphing toward understeer as limits approach, while the rear end stays well planted. The SRT team dialed back the stability control's intrusion level, and it can be switched off if you wish.

Automobile Magazine:
Geneva Show Preview Chrysler Crossfire SRT-6 - News - Automobile Magazine

The Crossfire is the first Chrysler to join the SRT ranks, joining Dodge's Neon, Viper, and Ram. Like it's corporate brethren, the Crossfire is packed with more power. Motivation comes in the form of a 3.2-liter supercharged V-6 making 330 horsepower. Sound familiar? It should — this is the same engine found in AMG-badged Mercedes-Benz vehicles

And many more . . . .