I would never buy a pre-built going off my mates.
It was swimming in thermal paste. I had to clean his board and some even got onto the underside of the old cpu as it was dripping down the sides onto the mobo when we upgraded CPU's 2 years later.
Then he also had the issue of it broke in transit when it was new. I think the GPU broke the motherboard due to pressure and movement. it bent / snapped some stuff. it took over a month and several call outs to resolve. over the phone their diagnosis was maybe the PSu so they sent a new one. after swapping that out still dead. then new mobo fixed it.
Then you have the additional costs, etc.
I'd rather buy everything and have someone local build it for me so I could learn and watch them do it. I have built many pc's and after I slated my mates machine he is never going to buy another pre-build. he would rather now pay me to build for him. his bro had to upgrade the motherboard after i did the cpu due to crashes and he slated the pre-builds use of cable ties was excessive and everything was hidden anyway. so it made the job a lot harder for him as he had to cut them all off when they weren't needed in most places. so after both me and his brother slating it he won't be buying one again.
i'm sure they also installed the ram in the wrong slots.