rca to xlr - best way?

connecting a sub out from my receiver to a sub amp. receiver output is rca, but the inputs on the sub amp are xlr. what's the best way to convert? adapter? a cable? does anyone manufacture cables that convert rca to xlr and vice versa? really could use some advice, as well as an explanation as to the benefits of xlr connectors. thanks
www.interlinkhouse.com They do Stealth Cables XLR>RCA or vice versa. Call Serguei Timachew he will sort out what you need.
Or....any manufacturer will make whichever model cable you prefer with the ends that you like! Also...there are "adapters" that you can purchase that convert RCA to XLR. I believe that Cardas makes one. I just bought an XLR (source) to RCA (amp) from www.fatwyre.com.....they made me one from Wireworld eclipse CHEAP!!! and had it to me in 5 days. I bought a cheapie because it is for my headphone amp. I think too much of my equipment to use an adapter (adapters seem to go against the "simple circuit" theory behind high end audio), however, I know high-enders that do use adapters with no/litte degredation.
If your sub is a long way away or has a potential ground loop (ie plugged into a different electrical circuit) you should would be best to use a transformer to convert from single ended to balaced. Then run an inexpesive balanced line to your sub. The transformer will balance your line and match the typical impedence of a balanced line. This will reduce potential ground loops and you will benefit from the common mode noise rejection provided by a balanced circuit. Blue Circle, Rane, and a bunch of companies that specialize in studio or professional audio make them. For a subwoofer appication you don't have to spend a lot.
Deepblue has a point. Balance is just that; not the same as unbalanced. Just using an adapter may cause problems and even degrade sound some. Good Luck
balanced lines *can* be quieter in long runs. if it's not a problem for you, neutrik makes xlr-rca adaptors in any configuration ya want - m-m, m-f, f-m, f-f, etc. i got 'em at my local pro-music store for $6.50 each. doug
look up RANE at www.rane.com , they have two units for coversion...Rane BB 44X Balance Buddy and the BB 22 Balance Buddy....there a maker of pro and consumer equalizers and other products.