Good question.
Here's the thing, if I was tight for cash and needed a cheap, but decent, car I would definately try and pick up a D8 Petrol Turbo - no really I would.
However, if I had some decent money to spend I would go BMW/AUDI. These would give a quality bonus but the BM would have to be chosen wisely cos they can make you look a w**ker and the Audi's are not the best 'Drivers' cars out there
f*ck it, I think I would go for a Vauxhall Monaro V8
As you can tell I don't know. I would hanker after a high quality interior BUT I would want a powerfull but tidy handling car too.
Pris - Don't try to convert yours to a V6 it would be more trouble than it's worth. Just buy one that is already a V6 and be done with it.