Having owned a c63 and now an e90 m3 I can help you there. ISF, fwiw, is not even in the same category. But before you take anyone's word for it, go sit in one. It's tiny in there! So all else aside, if you're looking for more room, pass on that.
You may want to add an Audi S4 to the list for comparo sake, but obviously we're all a bit partial to the bimmer.
The C63 is a fantastic car. As far as automatic tranny cars go - it's one of the best. But it's still an automatic at the end of the day. On the BMW, it's an "automated" manual. The DCT as a transmission is a work of art. It shifts so dang fast, it's truly amazing. I'm a die hard rower having only owned manual tranny cars (plus the c63) throughout my life. After DCT, I don't want to go back. It's truly the best of both worlds.
I would suggest you aim for the youngest you can find, 2011, e90. They are somewhat easy to find right now as people finish two year leases and those bailing in prep for the F chassis. The irony, however, is that all my life I've looked for manual tranny cars and for some reason, now that I was shopping for a DCT, all I came up with is MT. Previously it was the other way around of course.
I found an e90 at Bill Jacobs BMW in Naperville, drove out to see it and it was sold in the time it took for me to drive there from Oak Park. I ended up shopping on cars.com, finding a car in Minneapolis and driving up there to buy it. Totally worth that hassle too!
In Chicago, the dealers to work with are Patrick, Bill Jacobs, Elmhurst, Laurel... the others are decent, but the north shore guys tend to be snooty (I've had to complain to BMWNA about one sales rep in fact due to the attitude in the past) and the one in the city, well, go read the Yelp reviews to get a taste.
PM me if you want some more tips as I just went through this exercise. Best of luck!