If you buy one of those new Eclipses with the intention of trading it in, be prepared to completely lose your shirt on trade-in. They depreciate VERY quickly. I have known only ONE person out of at least a dozen eclipse owners that didn't get completely screwed when selling their eclipse... and that's cause she sold it to an individual instead of trading it in.
as far as GS-R versus ITR goes, there's like a 1/2 second difference on 0-60 and about a second difference on 1/4 mile. Either one will take an eclipse GTS and its "210" (dealers say "203", I say thbbppt) horsepower straight back to school.
Take a GS-R, give it a cold air intake, a 2-minute timing adjustment, and good tires, and the eclipse will be beaten by a car that supposedly has 40 fewer horsepower.