I would highly recommend that you don't buy anything until you can confirm that whatever type of adaptors you buy won't cause problems or even damage your system. Typically, XLR jacks and cables are used on balanced equipment and rca on single ended gear. These 2 modes of operation are not compatible. A balanced connection requires 3 conductors. 2 hots (++) and a ground (-). Single ended connections require 2 conductors. One hot and one ground. You're going 3 into 2. You need to do something with the extra signal conductor. Most adaptors shunt the number 2 pin to ground. When you combine one of the hots from the balanced side with the ground, you create a short circuit if you plug the adaptor into a component that's outputting a balanced signal. Its like disconnecting your speaker cables and touching them together while music is playing.
There are different ways a balanced connection can be wired. You can use an adaptor in some cases, but you must make sure its OK before you do it. If your balanced component floats the ground, you should be able to use the adaptor. If not, you're going to get a short circuit. Check your owners manual for the balanced component and see if they give you instructions on how to make it work for unbalanced operation. If the info isn't in the manual, call the manufacturer and ask them if its OK to do it.
Assuming its OK to use an adaptor, the thing to remember is when you mix the components, you end up with end up with a single ended connection. Use a regular pair of rca cables, along with some xlr to rca adaptors. Purist and Cardas both make high quality adaptors. I would use either one.