Welcome to Audioholics. Asking questions about home audio is always a good thing. No questions are dumb questions, unless you never ask them. Some newbies find it difficult to admit what they don't know. I'm glad to see new posters at AH, such as yourself, asking plenty of questions.
Verdinut, Bobby Bass, and others have already pointed out that balanced audio connections with XLR plugs are not really needed. But, here's a bit more info about XLR connections…
Balanced audio connections are commonly used in professional audio for live audio and in recording studios for microphones with long cables. Microphones produce very low voltage signals, 1-3 mV. Long cables, 30 feet or longer, carrying such low voltages can easily pick up noise from electromagnetic interference (EMI) or radio frequency interference (RFI). So, audio cables carrying low voltages over long distances should be balanced to cancel out this EMI/RFI noise. They must also be used with audio gear that come with the differential circuits required, on both ends of the cable. Read about it here:
http://en.wikipedia.org/wiki/Balanced_audio
Years ago, Pro Audio, standardized on balanced audio interconnect cables with sturdy, locking XLR plugs. Pro Audio often needs to use long interconnects, such as for microphones, and works in a wide variety of locations where EMI/RFI might be a problem. Eliminate any confusion from having both balanced and unbalanced interconnects, by having only balanced ones. XLR plugs & jacks are sturdier and will stand up to wear, tear & abuse better than RCA plugs. All are good reasons, for those in pro audio.
In home audio, RCA plugs & jacks became the standard type of connection because they are inexpensive and small. XLR plugs on balanced cables (3 conductors, not 2) are larger, and the differential circuits needed for balanced connections cost more. Why use up limited space on the back of any receiver with larger XLR plugs if it isn't needed? Why add to the cost if it isn't needed?
Interestingly, phonograph pick up cartridges also produce low voltage signals, about 0.5 to 5 mV, similar to the 3 mV signal of microphones. Yet, all turntables rely on unbalanced cables with RCA plugs. As long as they're not longer than 1 meter, 3½ feet, they're no problem. In fact, I've never heard of a turntable that requires balanced audio connections with XLR type plugs.
RCA interconnects are not balanced, and can pick up EMI/RFI noise if it's strong enough to interfere with the desired audio signal. It's important to understand that short enough cable length, and high enough voltage level of the audio signal can both make an interconnect cable effectively immune to EMI/RFI noise. Despite what you may have read, most homes do not suffer from high levels of electronic noise. There can be exceptions, but you'll know it if your system picks up EMI/RFI noise. It isn't subtle.
Balanced audio connections have become fashionable among audiophiles for use at preamp-to-amp connections. It's almost never needed, and it's odd that people have been misled into believing it's valuable – valuable only as audio jewelry. There are lots of examples of electronic gear that feature XLR connections as a sought-after feature, usually at higher prices. The voltage levels between preamps and amps are about 0.1 to 5.0 volts (100 to 5,000 mV) – much higher than microphone or phono pick up levels. Interconnects at this level carry signals that are about 100 times stronger than a microphone or phono pick up. Standard unbalanced RCA interconnects between a preamp and amp are fine, unless you have an unusually noisy environment with high levels of EMI/RFI.
