I've owned my XFX RX 6600 for about 2 years now and it's a great card but making the step to 1440p has limits. In my opinion PC gaming is in an almost ridiculous place ATM with prices and marketing so...
Also thanks for any help and please explain why you suggest a certain GPU. New or used doesn't matter.
I sill really like the 6600 as it runs quiet and doesn't draw much power for most of the games I own but it's just the few I play regularly now where it struggles.
I regret not getting a 6750 XT last November when the price was good.
If power consumption is a concern, you can manually tweak your power consumption in AMD's driver. I like to stay under 200 watts for GPU, so I undervolted my 6800. Since most chips nowadays are pushed well past their efficiency curve, it took just a minor undervolt and a minor underclock to cut my power consumption by half. My 6800 currently pushes more frames at 1440p with lower wattage than my previous 6600 at 1080p. Although, you do have to have to have the time to sit there and try different frequency and voltage values.