chino and chris have pointed out some good directions for you already.  Re:I would like to upgrade the graphics to the best possible graphic card, which can be used in this computer best can mean best compatible with cpu and psu.  the stock 460w psu can supply one black 6+2 pin pcie connector which is good for gpu that needs a 6 or 8 pin.  any higher power gpu that needs two 6 pin, 6+8 pin or 8+8 pin would be too powerful for the stock psu. if you do not plan on psu upgrade, best nvidia gpu would include RTX 3070 (psu below) or below Load Wattage:430 WRecommended PSU Wattage:480 W beware that the intel 4th gen cpu will bottleneck modern gpu (20% for 3070).  if you plan to upgrade desktop in the future and continue to use the gpu, then it makes sense to invest in a future proof gpu, if not then consider an older slower gpu such as gtx 1070.
Can you help me upgrade the graphics card in my XPS 8700? It's 10 years old but works perfectly. Spec is 4th Generation Intel Core i7-4770 processor (8M Cache, up to 3.9 GHz). It's equipped with the original NVIDIA GeForce GTX 660 1.5G GDDR5 graphic card. I have upgraded it to 32 GB RAM and an SDD hard drive.  I would like to upgrade the graphics to the best possible graphic card, which can be used in this computer. I'm used to change things in my PC, but this issue is complicated for me. Can you help? Thanks, Jesper
XPS 8700, best graphics card upgrade?