Uh oh, you've asked a good question.
http://www.antiqueradios.com/forums/viewtopic.php?t=153833More basically, clip with cutting pliers the connector plug off the end of one of your computer speakers if you don't want research and purchase adaptor plugs.
Follow the guidelines in the above thread.
Depending on the model year of your RME 45 and your construction skills an electronice knowledge you many need help on this one. Looks like there's variance in the solution depending on model year. You need to trace out the receiver to see if it requires a field magnet coil type of speaker and a resistor substitution for such.