If u want speed, buy a RSX-S, it can be fast, depends on what u do to it.
If u want comfort, get the G35 Coupe. Its what the new Skyline is in Japan, but it is way too much weight to be called a Skyline. But it is very comfortable. It has the same V6 287hp engine as the 350Z, just lot more weight. It is faster than the RSX, but after $10000 into both cars, RSX-S wins because its lighter = faster.
Or if u want both style and speed, find a 6cycle IS300. It can be fast with the Jackson Racing SuperChager system on it, and its very comfortable, very.
G6 is some what ok, very bad on gas, very bad on weight. Tho safe, but engines can't be trusted, have to go by luck.
A4 is comfortable, expensive tho, but very nice engine, last very long. Engine can get up to 300hp - 400hp, but repair parts cost more.
the other toyota i have no idea, the BMW I only played with the type 5 roadster, that thing is the top BMW out right now, but all of their cars are very nice and reliable, speed is up to u.
I only played with the RSX-S, G35, IS300, GTP(similer, but alot better than G6) and the A4 in the list you metioned.