Turbocharging an M113 engine

[donkmeister]

I have a 2004 E500 that has recently had its 100k mile birthday, so it has recently achieved "finally properly run-in" status. I would like more power, and am considering upgrading to an S500 4.7TT or even an S600 if the right one comes to market, but at the same time my E500 is a known quantity, worth very little to sell but has so much left to give... I can either spend £20-30k on one of the above, or I can spend £2-3k to get more power out of my E500 to keep me smiling for a few more years.

To me, the obvious options are:
1) Nitrous: cheap, but a mate who used to run nitrous on a Supra reckons I'll empty the bottle far too often and it's going to be a false economy.
2) Supercharging: Kleemann kits are like hens' teeth nowadays, and would be well out of my budget. So, really I'd be better off buying an E55K engine and fitting that but I'm not keen on fitting an engine and gearbox of unknown provenance.
3) Turbocharging: I've seen some M113 turbo conversions online but they all have boot-mounted turbos. This is a daily driver and also our roadtrip car so I'd like to keep the turbos under the bonnet if possible.

Turbos look like the best option to me, but I don't want to have a very hot or non-existent boot. Is anyone aware of any E500s or similar models with aftermarket turbocharging that is not boot-mounted? Who fitted them, and any idea what the cost was?

[Fattyfat]

I don't think there'd be room under the bonnet for turbo(s) hence aftermarket conversions using remote mount.

Probably pick up a 2nd hand Kleemans stateside or look at selling what you have and find a nice E55