First: I wasn't buying new... this is my third car and isn't ever going to be a garage queen. I park it outside, I take it to the airport and Angel games, and I put my surfracks and boards on top of it. So that limited my choices as the RS5 was only available brand new.
Second: It had to be a four door sedan. I want to comfortably take my son anywhere/everywhere with me. That double eliminated the Audi.
Third: As good as some dual clutch tranny's are, I wanted a proper, three pedal transmission. That eliminated the IS-F and the AMG Mercedes and triple eliminated the Audi.
Fourth: My wife HATED (and I can't overstate that) the CTS-V. I actually got past the kind of crappy interior and loved the wonderful motor and great shocks in that car but she wasn't having it for a second.
The E90 M3 stands alone. So far, it's been a great car. My boy loves "Daddy's Double Oooh" and enjoys riding with me and that's worth more than I can describe. This car is comfortable, pretty damned quick, handles well, and is a great size for our needs. My big complaints are that the gas tank is too small (I knew the MPG was going to suck but combine that with a tiny gas tank and I fill up twice a week) and that it's honestly a bit too heavy. But for what I paid... it's a screaming banshee of a great deal and perfect for my needs.