Hello & welcome ( i really should be in Bed)
Now i'm a relative newbie myself but i did spend alot of time researching the IS200 before i went an bought an Altezza.....
It will really depend on the year you go for as well......
All have the same engine - 6 cylinder 153 bhp
All manuals are 6 speed, autos 4 speed
The S is the entry model, no leather, no sunroof, No sat nav, basic 16" alloys, no amp - 6 speakers
The SE is your Executive, electric sunroof, sat nav , leather seats option, better stereo
The sport model is slightly lowered and has standard 17" alloys ( nice), electric sunroof, sat nav option, better stereo, nice sports pedals too, some sports will already have a boot spoiler
It will really depend on the year, milage and any extras, but the S should be the cheapest and the sport the dearest
Personally I'd go for a sport with those lovely half leather seats !
good hunting
But if you want a bit of extra zoom, get an Altezza RS200 ( 210 bhp manual standard, 200 bhp Auto tiptronic ). :D or an IS300 with 211 bhp auto only !