Subject says it all…or maybe a PM?
PM first, then wheels.
You can rent wheels and you can use a pm on a trainer.
You answered your own question, “or maybe a PM?”…YES, a Powermeter first! You could go the powertap route, with disc cover and then deep front wheel and get both of your needs covered in one. I think JackMott posted either on Twitter, FB, or on here about a smoking Powertap deal the other day…