Ok, well after a couple of test drives, I have changed my mind about a lot of what's important to me. Apparently my tastes are growing up (a little).

-Apparently size does matter- for whatever reason the smaller cars just don't appeal to me, nor do 4 doors. The 4 doors don't feel sporty enough, and the roadsters feel too small. The G35 size coup is exactly on target.

-Comfort and "nice little doodads" are a lot more important to me than I thought. I guess I'm just a sucker for buttons and gadgets, but driving that Infiniti got me addicted.

-I am completely over wanting a Mustang. Not just because of the Ford credit thing, but I just realize I want something different from a car than sexy and fun. Obviously I would have said differently two weeks ago.

Bottom line, I think I can probably get a used "Luxury" car pretty well equipped for under 30K if I look hard enough and I will be happy and comfortable with both the car and the payment. I'm going to probably take a few months without a car payment before I take the plunge, but in the mean time I'm going to see what else is out there. There have been a lot of suggestions in this thread, but my focus is now a little more narrow and my goals are different. So I'm humbly going to ask again, but this time here is what I want:

A nice, comfortable car that I can get used for under 30K, is slightly sporty (meaning 2 doors, not 4), is really comfortable, isn't too small (the size of the G35 is perfect), and is well made an will last. Obviously a great sound system is a must (including a way to install an Aux in), and while doodads and gadgets are not strictly important, the certainly can sweeten the deal

Roadsters, wagons, 4 door sedans, and SUVs are all out. Just not what I'm looking for right now.

Are all of the BMW 3 series cars smaller, or do they make some more along the lines of the G35? I'd think that looking at used Audi's might be the way to go; are the models that music mentioned comparable to the G35?

It might seem like I've settled on the G35- truth is I sort of have. After having driven one I basically fell in love. I haven't driven the Audi's or looked at used BMWs yet, though, and I might like one of those even better. Besides, two weeks ago I was settled on getting a brand new Mustang, which I now know would've been a mistake. I'm also not sure I'll be able to find exactly the car I want used, so it'll be helpful to have more options. Thanks for all the help so far- this is an awesome forum.