I've been reluctant to mention the speakers I've been using. (with good reason)

Several years ago I bought a pair of Matrix-MX1300 speakers for $75. Yes I know they are "white van" speakers. I'm by no means an audiophile but they sound great- especially with my new Pioneer 1020k.
Regardless, I'm concerned about the impedance curve which could possibly drop too low and damage my new receiver. Is there a way to test this? Or should I just replace the speakers? Or perhaps I could keep the housing and replace the drivers / crossovers?
I'm just concerned that it's going to take a lot of money to reproduce the quality of sound that I have now.