msrp is the price that the manufacturer say the card should be sold at, usually it is lower than the actual price depending on the supply and demand and on how much the retailer want/can make on top of the base price
For the chart, it’s readable this way:
the higher ↑ a gpu is on the list , the stronger it is. you can see that being on top of all the others, the amd rx 7900xtx, nvidia rtx 4080 and nvidia rtx 4090 24gb, are the most powerful gpu’s of the chart, the best one of the 3 being the nvidia rtx 4090 since it is above all
you have 3 big columns one for amd, one for nvidia and one for intel.
wen a gpu is on the same horizontal line as another, even across the columns, that means they perform roughly the same.
For example:
the nvidia gtx 1660s that you have is on the same line as the:
amd vega 56, nvidia rtx 3050, nvidia gtx 1660Ti, nvidia gtx 1070Ti and the intel A580
So all of those perform roughly the same, if you go one line above, those the cards on the line will perform slightly better, 2 lines, a little better, 10 lines, much better etc
you can see with the chart that the closest modern amd gpu to your nvidia gtx 1660s is the amd rx 5600xt, but since it’s only one line above the one you have, it is only going to be slightly better than the one you have.
what you should do is open the shop on which you want to buy the card and find the card that is the highest on the list in the amd collumn that you can afford.