re my 750ti
" The prices of second hand 980tis (for instance) have gone up considerably recently "
Yeah - looks like i picked the wrong time to upgrade. I shopped around I started out thinking I might get an secondhand 8 or a 9 . Did loads of reseach , looked at performance graphs etc
https://www.geforce.com/Active/en_US/shared/images/products/shared/lineup.png
My conclucsion: "Blimey these things never lose any value! - I'll just get the bottom end 750 , thats nearly falling off the bottom of this chart - its still better than an AMD EAH5570"