Just traded my RX-8 in for the Z today!
and coming from an 2000 Audi TT 180 and Mazda RX-8, i can only urge you to go and try the Z! you'll absoluetely love it!
the TT was the slowest car that i've owned. Mazda RX-8 was not bad, but it was gas and oil thirsty!!!! i would only get around 190miles per tank (well, i take it to red-line quite often. but that is how you're suppose to drive it anyway)