To those who have removed and replaced the factory MACH 460 6"X8" or 2.5" speakers, what's the impedance on them? Is it printed on the speaker anywhere? 2 Ohms? 4 Ohms? 8 Ohms?

I want to replace my factory speakers with aftermarket ones. I don't want to go the whole nine yards and replace the amps and head unit yet. I just want to replace the speakers for a low-cost sound improvement.

Thanks.