I am German.
I have over 400 horsepower.
I get from 0-60mph in 4.4 seconds.
I have a V8 engine.
I have a standard navigation system w/voice recognition, power rear sunshade, leather upholstery, and way more.
I am one of four. The other three look identical to me. Two of them have V12's, and the third one has a V8.
My price is closer to $100,000 than it is to $200,000, but closer to $150,000 than it is to $100,000.
The sum of the digits of the amount of horsepower I have is the sum of the value of two sides of an isosceles triangle, each measuing 7.
I can seat five adults.

Who am I?

audi R8

Mercedes-Benz S63 AMG

__________________
2003 Ford Mustang SVT Cobra
4.6L DOHC V8 - 6 speed manual
520rwhp - 525rwtq at 16psi on stock blower
2002 Ford Mustang GT
4.6L V8 - 5 speed manual

correct, apolloGT

take a look at the last hint
the r8 is $115,000
the r8 has no v12 twins