WHERE do you go when your budget is on the right side of $200,000 and you want to combine pure luxury with nonchalant power and supreme on-road agility in an occasional four-seater with a convertible roof? BMW’s soft-top 645i might just have the answer. Apart from the fact it’s expensive, there’s not much about this car you can fault. The 4.4-litre V8 engine means it pulls like an express train while the "active" suspension and steering helps combine an absorbent ride with the handling of a go-kart. It might not be a member of the emerging full-metal convertible push but, with the roof up, passengers would be pushing to separate it from its coupe sibling.