It is possible if any of these conditions are met:
1) your speakers have speaker level inputs (not likely)
2) you can convert speaker level signal to low level signal (again not likely)
3) your receiver has preouts (hopefully)
I would not recommend trying to rip out the amps in your speakers. It wouldn't yield the best results. It's feasible, but why would you want to do that?
The best scenario for you here in my opinion would be if your receiver has RCA preouts. Then just connect those to your speakers and use them as the mains.
By the way, RCA to miniplug will work (I'm assuming your speakers have miniplug inputs, like on a portable CD player?)