Charging the HR is quite expensive, £7k min for self install if you do it on a budget, but realistically you won't get much change from £8-9k. It will be a lot cheaper to go for an earlier model and do it. The Zed handles well out the box, but improves massively with a few suspension tweaks.
Like Ekona said, the M6 is a awesome machine for little money and will destroy most things on the road! And the 335i and M3 can be picked up for similar money. Depends what you are after at the end of the day, everyone has a BMW these days the Z is something you don't see many of.