How do you sell a still powerful but not top of the line anymore computer

Hey everyone, as Christmas nears I'd really like to overhaul my gaming rig which is already 2 years old. It can still play most recent games at high or max settings, but having cash on my hands I'm considering reselling it as a whole and buying a whole new rig.

First off, I know I could update the key parts of my current computer (processor and graphic card) to give it a significant boost, but this would mean getting rid of components which still work great... That's why I would like to resell my computer for a fair price and upgrade to a better, more powerful one.

Thus, the question is : how do I resell my PC ? What's the most efficient way to find a buyer ? I feel like putting it on eBay will not work since there are already so many similar offers... I live in Europe, so there are websites like Craigslist but I'm not sure it's the best place to sell tech articles (but I could well be wrong).

Maybe I've got it wrong and I'd better resell the components apart, but is there a way to sell it as a whole (for the sake of conveniency) ?

I feel like my best bet is to find a friend or relative and offer them a compelling price.

Any thoughts on the matter ?