Hi and welcome to the club. Before I start, I’d just like to say that I’m no expert on this subject, but from what I can gather the engine on the IS200 is fairly bullet proof, as long as it’s serviced by competent mechanic.
FYI, there is a sticky in the IS200/IS300/Sportcross section with all of the specs on the different cars in the IS range. This will tell you everything you need to know.
I noticed a couple of the cars you have singled out are automatics, which will be more thirsty than a manual, especially in built up areas as you are stopping and starting in built up traffic etc.
Also I believe a couple have the IS Sport pedals, which may indicate that they are indeed Sport versions or they may have been put on by the current owner as an aftermarket thing. If the insurance is so high on a sport, it may be worth while checking with the sellers that they have their information correct before you seriously consider the car.
As for the insurance, try “A Plan” in Andover on 01264-365536, they seem to be cheaper than anybody else I have spoken to and may be able to do you a deal.
As for my choice out of the ones you picked, I do like the PISTONHEADS one and I also like the one with the aftermarket stereo system. If you look at any car with the CD loading slot at the bottom, it will potentially have error 3 codes, so you may end up changing the system anyway!
Anyway, good luck and make sure you post your pictures when you finally get your new wheels.