Yup I agree this is probably the most mature discussion we have on the srt-4 vs. msp thread ever on this forum. I have to pick upgrading engine over suspension and let me explain before people flame me on this.
1. I work on engines for my daily living, I worry about multi-million machinery that cranks out XX,XXX hp. So engine aka thermodynamic stuff is easier for me to comprehend.
2. To do a suspension system properly you have do to do the whole thing. Experience what an aftermarket car feels like and a stock well-tuned suspension feels like. The stock suspension system is a compromise but it handles well. Now that being said, if I ever get a SRT-4, I would have to redo the whole suspension system to fit that much hp. That's major $$$$$, I'm talking about changing suspension geometry, parts, spring rates, bump stops, alignment, and chassis stiffening, and contact surface.
3. MSP suspension is well design for street everyday driving and spirited track driving. It's a fwd so too much hp on it is useless anyway. Right now, I'm looking into pumping up my msp but more along the top end with a nice straight hp and flat torque curve. This motor does not have a very good top end. This is shown for example in Brian's latest dyno. He's a forge motor and new turbo, but his tq curve still falls off at the top end. I want to maintain that peak. The suspension of this car will allow this power pump no problem.
4. The turn-in of this car is simply amazing, granted it can power out like an evo, but I bet it can enter the corner at the same speed.
5. The balance of this car is aboslutely the best thing you can get at the price range of this car. weight transfer is so easy on it and the car responds very well and communicates very well.
6. HP isn't everything, unless all you live for is 1/4 mile at a time. It's weight transfer and putting down usable power that wins, look at s2000.
lastly everyone talks about car to trade for msp well for me there's like 3:
lotus exige, rx7, or a mr-s with 3sgte.
SRT-4 = fast car, but not balanced.