Another issue that I haven't seen anybody mention here is ergonomics. I suppose this is just a special case of practicality, but it's worth thinking about. By ergonomics, I mean everything from whether you can get in and out of the car comfortably to whether the air controls are easy to use without taking your eyes off the road. This is traditionally where American cars fall flat on their faces (particularly GM products) and where Japanese cars shine. I just test drove an Acura TSX yesterday, for example, and I was really impressed with small things like the turn signals and the beautifully readable gauges. The navigation system also has a clever push-to-talk button mounted under the steering wheel, and the voice recognition system works remarkably well.

If you get the TSX, you're still in the same financial ballpark as a 350Z or a WRX STi (well, several thousand dollars cheaper, but still...). The trade-off is better "luxury/ergonomic" features versus better performance features. One prime benefit of the WRX STi, contrariwise, is that it comes without any stereo, which makes it straightforward to add your empeg. That's much harder (maybe impossible) to do for the 350Z, and it's tricky for the TSX.

It's all about trade-offs. A Lexus IS-300 or Acura TSX (or BMW 3-series, or other European sedans) doesn't give you as much zoom for your dollar, but you get better craftwork on the interior, useful trunk space, and all that. Of course, you can always do an after-market super-charger.

Meanwhile, the other issue that I don't see you raising is reliability. We've talked about it at length in other threads. I'm curious if reliability is one of your criteria.