Just my two pennuth but could it be that the GTL graphics engine, being so old, simply doesn't have the capability to respond to modern day graphic cards bells and whistles?
Maybe some of the new features Tony, but AA and AF was around when GTL was new, and it's all I've used to affect the graphics. Supersampling which I ended up using, has been around for years, but my earlier videocards weren't fast enough for me to use it - it's apparently a 'brute force' kind of method, requiring a lot of horse power. The Sapphire card I'm using is based on AMD's RX 480, is quite new, and an 8Gb card like Clive's, so if I can get an improvement, I'd expect it to be possible for Clive too, even if AMD & Nvidia has different approaches.