No problem at all - but check the impedance ratings first, your speakers might be 4 ohm (should read on the back in the type label) and your amp might want at least 8 ohms. I'd expect it to accept anything between 4-16 ohms, though.
If the speakers have captive leads and the DIN connectors are still there, you'll have to decide if you want to cut them off, or purchace / build adapter cables. The amp most probably has screw connectors. The original DINs would be handy, though, once you get a nice vintage B&O receiver to replace the Pioneer 
And welcome to Beoworld!