If your not bothered about the MPG,then id go for an E60 M5 Touring. The sound they make is amazing,and im an AMG fan! Depends if you can get on with the gearbox though. I know the AMG auto box is meant to be pretty good,and the SMG2 in the M5 is supposedly abit clunky. The other option is the RS4,as i think the RS6's,the V10 versions anyway,are still at £40k. Depends how much space you want really. Iv never driven either cars,but id find it hard to choose between the BMW and the E63,those would be the 2 on my short list of that size car. I was strangely looking to see how much M5 Tourings go for today on Piston Heads.