it depends upon which card you want to buy because everything has a price floor like used 1060 still sell around 12-13k because there is a low price limit and most of the lower end has been abandoned by both nvidia and amd.
yes they are getting cheaper and will keep getting cheaper but those drastic price reduction will happen at top end , you can even see now lower end is slowly bottoming out and stil selling over MSRP atleast the nvidia cards.
so cards like 6600 might get cheaper by 3-4k at most now at 23k its great deal its already selling below the MSRP of 6500xt at this point, so if you're thinking of buying this go for it , however would not advise you to buy higher end cards like 6800xt or 6900xt or 3070 ti's and above they will see further price drops.
you can buy this 6600 and still sell it after 6 months for 18-20k on used market easily and upgrade to a used nvidia 3000 series card or 4000 when they come.
you can use online PSU calculator
here is the most used one
https://outervision.com/power-supply-calculator
just enter your hardware and overclock settings and it gives a goo estimate about your wattage, there is similar tool by cooler master and other PSU vendors which also recommend PSU based on that you can search those.
general rule of thumb is to keep 200-300 watt headroom when buying a PSU for future upgrades because PSU tends to last longer than most components.
