You will need a PSU upgrade for the 12GB 3080, 3080ti and also a 3090. Your 650w will not do for any of these cards.
A 3070 is the max I would use on that 650w psu.
I believe @MissChief is running his 3080 on a 650w just fine?
I hope your choice is satisfactory. Good choice on the 3080, more than enough grunt for 1440P.
Depending on what fps you're happy with and what settings one is willing to use, a 3080 does not have enough grunt for 1440p for high refresh rate gaming, it's fantastic for 60hz but not 100+hz/fps. I have several titles where even with dlss quality/balanced, it doesn't achieve a locked 80 fps (my ideal fps limit) especially in RT unless sacrifices are made to settings. However, what I will say is the latest version of dlss is fantastic on performance mode if you really want to push fps without sacrificing graphical settings, a lot more usable than when I last tried it, at least this is in cp 2077 anyway.