If you're going to have ridiculously impractical dreams that would be prohibitively expensive to make real why not go all the way. Dream of putting a V8 in it.
And, seriously, there are a couple of physically small and lightweight V8s available in Britain for track car and motorsport use that are built out of pairs of motorcycle engines on a common crankcase. Because they're not huge displacement they don't need a big gearbox, but they produce lots of horsepower. Lots more than you could get out of a Renault V6. Because they are only 4 cylinders long you could fit one crossways across the front of a Clio with a gearbox on the end - a sequential box would be nice. It'd be a stunningly quick car with 3-400 bhp in it. And imagine how it'd sound when you wound it out with a V8 revving to 10,000 rpm.
http://thekneeslider.com/archives/2005/02/09/hayabusa-v8-engine/
Look at the guy's hands in the photo to see how tiny a motor it is. And it produces 372 bhp. That's 12 second times for the quarter mile, 0-60 in the 4s, and a top speed of about 175 mph.