I didn't really want to step in on this argument, but I'm gonna make a couple post.

Firstly, a fully loaded IS350 is about 45K..... How is the difference between it and the IS-F $25K?

 

In your opinion, is the M3, RS4 and C63 worth the upgrade over their respective counterparts?

It is pretty much the same thing.......

 

I paid $34,200 for my IS350. The only options were the 18" wheels, spoiler and trunk net. No need for Nav as I do not live in a big city and no need for Sport as I planned on lowering it anyway. After the wheel/tire/spring upgrade I have $37,000 into it but should get most of that out when selling the wheels before selling the IS350. I would also look at a bare IS-F but pricing hasn't been announced. I estimated $60k based on the $65k NM edition. I would also change the wheels on the IS-F if I get one.

I am also not looking at total cost of ownership because I cannot predict the depreciation rate of the IS-F. The IS350 is looking very good so far.

 

Interesting question. I haven't driven most of the cars except the 335.

Cliffnotes:

M3: Unsure but probably not worth the upgrade compared to a 335 (unless the M3 is a blast to drive and the engine is truely that special)
C63: IMO, yes it is worth it based on what I know.
RS-4: Unsure but it probably is worth the upgrade based on my experiences.

M3/335:
There are several discussions on the BMW boards about "why buy an M3" when the 335 is so good and able to be modded easily? Pricing is also less of a difference as a 335 is $5k-$10k more compared to a base IS350 while the M3 and IS-F are comparable. I haven't driven an M3 so I can't make a decision yet. Reading about the 2 cars would seem the 335 is the best choice. Stock vs stock, it beat a Z4M around VIR. It can be upgraded to be faster than an M3 in a straight line. But is the M3 more "fun" to drive to me? I don't know yet.

RS-4/S4:
I haven't driven an S4 since the B5 and I only had the chance to sit in an RS-4 at the NAIAS and was very impressed. S4's are much more expensive than IS350's and I've heard the RS-4 is a blast to drive. The 6spd gearbox blew away the 6spd gearbox in the M3 (BMW still retained the E46's POS gearbox for some reason).

C63/C-class:
Based on the feedback available, the C63 looks to be the stand out. Over 450hp and there is not a comparable "sport oriented" C-class (add on "amg" fenders don't count!) that would compromise sales.



Regardless of my opinions, each person must drive the cars you are comparing before making a decision. My first shock came when I was dead set on an '93 Rx-7. After driving it and then driving a '93 300ZXTT, I chose the 300ZXTT. It went against everything I had read online but I enjoyed the 300ZXTT a lot more. I still wish the Rx-7 felt better because I liked the looks and specs (mainly weight and redline) a lot more!

 

That's just awesome that Lexus did that, it shows where the focus of the car is. Wish I could have joined you!

I hope they do it for the LF-A!