Well given saving money at the moment is pretty much pointless given the rubbish interest rates you have to do something with your money!! I've gone down the mortgage free route, on course to be mortgage free in a few years and than I can think about a better car....Ofcourse by than kids and the need for bigger house (with a bigger mortgage) will likely to be top of priorities list
Enjoy M6, but it just seems a bit boring compared to other cars you've owned, cannot wait to see what you replace it with
....what about a stupidly priced updated/restored classic like a E-Type??