A lot of interesting point there Damo, particularly the brakes. Yes, they should be upgraded but are more than capable of stopping up to 200bhp as standard if you have the 282 x 22mm vented front discs and standard rears - don't forget you don't want anything too good on the back because of weight transfer during braking, all the weight goes to the front so that's where you want the better braking.
The handling is a bit more subjective, a lot depends on exactly what you plan on using it for.
For normal daily driving, most 7/9xx are fine as they are, a bit wallowy if you get a bit "enthusiastic" but always predictable and safe, it's seriously hard to get the back end to break traction without being very brutal and even then it usually recovers itself quickly.
Uprating the springs would reduce the body roll or doubling up on anti roll bars would also reduce it while maintaining the ride comfort.
Lowering springs will drop the centre of gravity which is always useful to improve roadholding and handling. Uprated dampers will control lowered uprated springs better as well.
Something often forgotten when making the suspension stiffer is to stiffen the upholstery. This not only improves your comfort but helps to keep you seated when you're hoofing it round a corner - on the standard soft(ish) upholstery, stiffer suspension will have you bouncing up and down in your seat like Zebedee on a pogo stick on acid otherwise.
It's always a good idea to make it stop and handle better before improveing performance, that still gives you a quicker car without having touched the engine.
As you say, the sleeper effect is great. Both my beasts have that, the 760GLE because people think it's a "normal" 7/940 until it leaves them standing with a 90 degree V6 howl.
My other beast (827 Sterling) does similar but has a 24v 90 degree V6 howl and accelerates a fair bit quicker than the 760 although that is no slouch either.
The Rover is viewed, particularly by the younger generation as being a "gutless 2.0 granddad car", ditto the 760 and they get a hell of a shock when they find that both have a 2.7/2.8 V6 lurking under the bonnet and the twin tailpipes serve a real purpose!
