A lot of nice cars there. They cover quite a spread of strengths.
The Boxster, well, it's good at everything but a master of nothing. Its got good power, good brakes, good handling, good comfort - nothing that really stands out though. It does have the Porsche factor if that's important to you.
The Vette is the "missile" of the group. Point and shoot, pins you to your seat, still comfortable for cruising. I personally love Vettes but in some circles they're not 'hip'.
The Elise, Miata, S2000, and MINI to me all are vaguely in the same category. Different flavors of a similar philosophy. Fairly quick, but their biggest strength is not in their power, rather handling/braking. So you have to ask yourself, are you the kind of person that loves to hear an engine burble and the thrust of a hard launch, or are you more into taking off ramps at twice the suggested speed?
The Jag is the oddball in my opinion. It's more about luxury than performance than the others. Yes it has performance but it's the tourer, the cruiser of the group. To me it says it says "I'm wealthy" more than the others which to me say "I like to have fun".
Good luck and keep dreaming.