I think the choices were already given in my previous reply. I am not going to tell you what to do. If you’re gonna buy PSE12 near its end-of-life try to find it on sale, at least.
One thing that hasn’t been discussed is what operating system you’re running.
If you have XP or Vista or OS X 10.6 then you cannot use ACR 8.4 or higher so you would not be able to use the newer ACR 8.x that likely ships with PSE13, limiting your choices to PSE12 and ACR 8.3.
If you have Windows 7 or OS X 10.7 or higher then you’d be ok with newer PSE/ACR versions.