Hi there, i am quite a big car enthusiast and work for VW as a tech. I have driven the RX8 (was a trade in) and i loved it. It was quick, agile and a comfortable car to drive (a little bumpy due to sports suspention). In my opinion the RX8 is more of a drivers car where as the celica is a little 'timid' for my liking. Although the RX8 is a better drivers car you will 'pay' the extra for buying, insureing and fuelling it. The Rotary engines in the mazda are very good but very thirsty so take this all into account when deciding.
Hope this helps

George