These are my opinions and i haven't actually driven the below cars, so purely from a subjective view of what i've seen and heard and everyone is different and has different views
BMW 335i/d M Sport Coupe-- No doubting they're quick, but if fuel wasn't an issue it would be the petrol, but.... They look boring to me and don't do it for me.
Audi A5 3.0 TDI/3.2 FSI Coupe-- I'd probably pick the tdi, nice V6 plus the option to remap it which should make it quicker than the 3.2??
Audi S3-- Don't know much about these so can't comment.
Mitsubishi Lancer Evo X-- Hmmm, quick car, but poor interiors and not that special.
Nissan 350Z GT-- Love the exhaust note on these, this would be my choice even though the interiors are no doubt lower rent than the BMW and Audi.
I like cars small,large, cheap and expensive, but i look at them as a throw away item, so spending large amounts on them and worrying about them getting scratched plus the bigger running costs of the more prestige models kind of puts me off spending more than i'm comfortable with.
I test drove two S4's last week, an 01 and 02, one was modded and the other not, both a nice place to be quick enough but dropping £6.5k-£7.5k on a car that won't get used much and can cost a fair bit when it goes wrong kind of puts me off them, maybe i'll buy one soon who knows :/
I even test drove a E60 M5, nice and quick in 507bhp mode but didn't feel that special to me, maybe because i wasn't interested in it meant that it didn't do much for me...