I currently run three cars, one of which is a 2006 M3 Convertible, acquired two years ago for about £24,500 with 12000 miles on the clock. The car was purchased from BMW Approved Used Cars on one of their Select payment schemes and now has 30000 miles on it. I now have the choice whether to pay £12,800 balloon payment; trade it in for a 2009/10 Z4 (2.3/3.0) or simply give the keys back. I like the Z4, however, BMW seem to be quoting £22k+ for an equivalent M3 to mine. The heart says go for the Z4, the head says buy the M3 or get rid of it. I have one eye on fuel costs but depreciation remains the bigger issue. I'd welcome your thoughts were you looking for a usable quality fun car.