No, you dont need a new PSU. The Corsair TX 650 is a good PSU and will push that system just fine. Nvidia recommends a 650 watt PSU for the 2080ti and those requirements tend to be on the high end. The 2080ti under load pushes about 30 watts more than the 1080ti. See power consumption in the link below.
https://www.techpowerup.com/reviews/NVIDIA/GeForce_RTX_2080_Ti_Founders_Edition/31.html
As far as RAM goes, Ryzen can be picky with RAM but the 400 series chipset has improved RAM compatibility a lot. If you want to be sure that it will work, go with RAM on the QVL as suggested above. If you dont go with RAM on the QVL, then just make sure to get it from a vendor who will take a return, just in case.
You bigger issue with the RAM may be getting it to run at 3400mhz without a lot of tinkering. 3200mhz is typically fairly easy, so that is the speed I would target as performance increase does not scale as well when you get much higher than 3200mhz.
What monitor are you using? If you are not gaming in 4k, then I would not recommend spending the money on a 2080ti. It is grossly overpowered for 1080p and 1440p. Even for 4k/60hz, you will be leaving a lot of performance on the table. The only way I would recommend a 2080ti right now is if you have one of those fancy 4k/144hz panels. If I were building a new rig today, I would go get a 1080ti on sale or even get a used one for cheap.
Then next year we will see how RTX takes off and I would look at the next gen RTX cards or see what AMD is offering. Buying a 2080ti right now comes with a very high early adopter price and for me I would rather hang on to my money considering a 1080ti will be able to push any AAA game for the foreseeable future.