Is there a cable maven in the house?

There are cables that will connect an unbal/RCA source to a bal/XLR input but there is not guarantee that they will work well in all situations. Cardas makes some as does Hosa.

OTOH, there are adapter boxes for this and these are much more likely to work fine with an RCA cable on one side and an XLR on the other.

The Jensen is excellent http://cgi.ebay.com/Jensen-Transformers-PC-2XR-XLR-RCA-Audio-Converter-/360356008112 but there are cheaper: http://www.google.com/products/catalog?hl=en&safe=off&client=firefox-a&hs=441&rls=org.mozilla:en-US:official&q=rca+to+xlr+converter&revid=1610109775&bav=on.2,or.r_gc.r_pw.&biw=1680&bih=869&um=1&ie=UTF-8&tbm=shop&cid=17143747499655455269&sa=X&ei=FhsJTsLIBMf20gHT0qCOAQ&ved=0CEkQ8gIwAQ

Just get the Jensens which have high quality transformers in them and which sound excellent by doing nothing wrong.

The PC unit listed above converts "Pro" +4dBu signals to "Consumer" -10dBV signals. I am not sure that is what you would want. I suspect the input transformers "PI" would better meet your needs, such as the PI-1RX meaning one channel per box (because your speakers are separated you will need two boxes) and also that it changes RCA signals to XLR. You should run very short XLR cables from the boxes to the speakers (no more than 1M). The best way to find out for sure what you need is to call the helpful folks at Jensen. Here is a link;
http://www.jensen-transformers.com/iso_aud.html

I have used both the BAT and Cardas adapters successfully. BAT are more robust -- but more expensive. Cheaper adaptors from other suppliers break easily.

Neal