i have an rx 550 which in benchmarks did 150-210 fps in league of legends very high preset but in my system it does 70-140 fps on low preset. i think the psu is holding back the gpu the psu is 250 watts the recommended was 400 could it be the psu's fault and if so how do know what to upgrade to? and if it will fit and if all the cables would be right im not much a of a pc guy but i know how to do some things.