to be blunt no u will not be satisfied with the is250's output, but will like the mpg better. get an is350 u want something similar with acceptable mpg. technically more powerful, but maybe a more muted sensation. others include a 135i as suggested, which gets decent mileage for the power. and as an upcoming college student i highly suggest something with a bigger trunk.
Bigger trunk to carry my books..? right? whats college like? lol
if you like the sound and power of the vq35 engine, you might be disappointed in the 250..i always had a thing with long cars so i never really liked the new IS's buttttt if you like them, then i strongly suggest getting the 350 since you like the power your 03 g gives out...you should also try looking into a g37S =] but whatever you choose, an IS is still a nice car in my opinion.
OOO off topic sorry but what seat belt thingy are you using?? cause my seat belt always gives me a huge and painful rash on my neck =[
Uh.. i got it at some asian auto store.. ^^ in SF we have a place called JapanTown for that kinda stuff.
How much MPG do you get with your 06 G35? more than 15..?