So the BMW and Merc aren't rated too highly then? :-? Did like the idea of a supercharger though 
If I could get insurance for it I would have a 540i or M3 straight away.
Seems I've been suckered in by their reputation; entirely why I wanted to pick your brains 
Also fancied a bit of a change and a more sportier car - thinking of which should I consider roadsters/ pure out and out sports type cars? Are there any decent, cheap ones out there?
Don't fancy FWD much, how does the Saab handle/feel with so much power through the front?
How fast is an MV6 - not on paper but in the real world? How much difference does the Mtek chip make?
Sorry for all the questions again 8-)
Advertising is a powerful tool Louis.

BMW and Mercedes... you are paying so much more for the badge... and the spares!
Supercharged Jag. Mmmm!

As others have said, hellishly fast (consumption is too). Downside is build quality and hideously complex electrics.
There are very few RWD sportier cars right now. It costs more to make them and people are used to FWD.
Nissan 200sx or 300zx. Toyoata Supra (1993>)? All RWD and rather rapid!

May take a bit of time to find an unmolested example.
The Saab only really gives away the FWD weakness of torque steer when taking off from a standing start.
In real world driving it is stunningly quick with good handling in standard form and easily modified.
Pick one without the troublesome traction control system (TCS) though.
Oh and in Aero form it has the best seats ever put into a car!
How fast is the MV6?
Against the cars mentioned above? Well you would not want to race them!
Difference is they are all turbocharged or supercharged so big differences in power.
What the MV6 does have in its favour is, it is cheap, handles well (especially with tweaks to the suspension), is comfortable, relaxed and has the best support network!

The Mtek chip makes a noticeable difference. It makes it more responsive from starting off and at the top end of the rev range and is a highly recommended upgrade.
Ultimately it is a question of how much you have to spend (include insurance costs here) and what you will be doing with the car?