I think you are looking at this in the wrong way.
You can buy an E46 M3 for 7k, or you can buy the best (non CSL) M3 coupe going for 25k. Thats quite a large difference for what is essentially the same car.
You can buy a Clio 182 for 2k or the very best (non trophy) for around 5k. The difference between the top and the bottom of the market is so small. You stand to lose 1k at most by over spending which if you have the money is an acceptable loss given that a 1k loss over a year of ownership is in the noise. Over spending a little (with a little sense) will remove all this faff.
If you have the money, cut all the searching and time wasting and just buy the cleanest lowest miles 5k Clio, or a higher miles Trophy, enjoy it and sell it when your done. Its still cheap fun which ever way you look at it.
These are more usable every day than an Elise (etc), for me that makes them more fun on the whole, I choose to drive the little 182 to work over other stuff that I own because its cheap, worry free fun. That argument exists on a 5k Clio to the same extent that it does on a 2k Clio the difference being the time you will spend by the side of the road at some future junction.
Like I said before, regardless of which direction you go in I wish you the best of luck.
Rob,