Here the G35 and the IS300 sport are about $5000 more than the MS6. I test drove the IS300. It was OK, but not great, and only 217 hp vs 274 in the MS6. I have driven my colleagues G35 Sport Coupe several times and been pwned by him the one time I went against him in the MSP. Very nice ride and pretty quick car. Much more impressive than the IS300, but I'm not sure the sedan would be as quick as it is larger and its power rating is slightly less (265 hp....I may be mistaken). If I was gonna spend the money that either of those cars cost, I would go with the STi, which is in the same ballpark here in Ottawa.
R