Hi. What gauge of speaker wire is recommended for surround speakers?

14 Gauge is the size you should use. 12 Gauge is too thick for speaker wire (some people will disagree, but it is, you don't even see it that thick in ultra high end cable). You will want to use a high quality oxygen free cable (not the stuff at Lowes) and you MUST use the same gauge for the front and center speakers. Just buy a 100ft spool of Audioquest X-2 or 14-2 for around $60 and you will be all set.

Gauge size should increase when length to the speakers increases. For 25' 16 gauge is sufficient, however if you would like better quality I would use 12 gauge.

I would use a quality, oxygen free, well insulated 12 guage wire for your entire system-not Monster; they're ridiculous on their prices and you'll never hear the difference.

16 gauge or better.

12 to 14 guage wire is all you need. Larger size (lower number) for longer runs. Edit: Not wrong, just had a brain fart.

12-gauge is overkill, so use any decent quality oxygen-free cable. It's really important that the cable is fully copper on both sides - if it is copper on one side and silver-y on the other, run away as fast as you can. Also, if you are using a powered subwoofer, you can drop down a size in wire gauge, especially for your surround speakers, since the subwoofer draws the heaviest current and does all the heavy-lifting -- and the powered subwoofer is wired internally, i.e., it only takes an RCA signal cable. I'd have to also say that, once you're using any decent-quality oxygen-free copper wire, the differences between various brands and configurations are relatively difficult to hear. Yes, the differences are audible, but not very easily - and you have to strain and stretch to maybe think you can hear a difference.