Tape output will work, but as mentioned you'll have to adjust volume individually on the back of the speakers.
The RussSound adaptor appears will also work (to allow you to use your receiver's volume control).
But note that the speakers are designed for a balanced input (XLR or TRS) versus single ended (RCA). So with either of the above options you'll need RCA (single ended) to TRS or XLR (balanced) cable adapters (not expensive to try). Hopefully going from single ended to balanced won't produce grounding feedback problems for you. I'd try the single ended to balanced adapters first and if that works you can also try the RussSound adaptor.