... i've been testing all resistors and matching exact values. But what do i know.
Definitely not as much as PRR. (who does?)
You have to determine where the exact values are important.
Even then... might be surprised what you can get away with, like i was.
Kev left this link on API thread yesterday, written by Mark Burnley:
http://www.diyfactory.com/data/mbresistors.htm
I matched components on pairs of pre channels to more easily distinguish differences between opamps and trafos. Why not? my first project, i figured anything hands-on would be good while waiting for other parts. Didn't take long. If they're on tape, it's easy to test them like that, and write exact values next to them. Easy for transistors too.
BTW if you get 1% tolerance resistors, you don't need to buy or test as many.
My (limited) experience so far with 1% Rs: at least 3 matched pairs per 10 resistors. Some values were equal x 10, at least to DMM accuracy.
But this probably also depends on brand, luck, etc.
hope it helps, Paul