My previous car is 2000 Maxima(built in 1999/09 and bought it with NTD480K in 2005 in very small used car lot in Taipei). Both my wife and I drove it in Taiwan.
I put Koni shocks + HR springs on my Maxima. In 2012 when my wife changed from 2000 Maxima(Taiwan) to 2010 M35X(USA). She said the new 2010 M35X was unstable and difficult to drive.
Of course my previous Maxima is not as sporty as your GS (stock form) because Maxima is FWD and had non-A front suspension and non-independent rear suspension. It only had pretty good steering from Infiniti.
So in my opinion if you are willing to modify, we will be very surprised how good your GS will be. Of course after modification, your GS will not as comfortable as now...