Thanks Artisan-West for the insight especially the 4GB card doing well...............my current card is 2GB, hence using CPU not GPU. In regard to tebel53 saying 8GB I see that that is noted on laptop/mobile devices 
As for the x0.5 the reason I remarked about downsizing i.e. it is not a 50% increase was that when imported and the button selected the X px by Y px dimensions shown on the GUI show half size image of the source size.
PS in regard to the graphics card ~ my system is not the newest and the PCI slots are v2 compliant. The one thing I have noted is that a lot of newer cards are PCI powered so could draw more power than the motherboard might be able to handle. A far as I recall my PSU is either a 750 or 850W one?
I now have an nVidia 1050Ti 4GB to hand but not yet installed. I look forward to seeing what sort of improvements in processing times I can see using the GPU processing rather than CPU.
PS sorry for the delay in replying but as a new member I had to wait for my 'access' to be fully approved 