cyrnel

Correct. The two wires should be colored or one will have a marking or rib. Use that as your key for positive or negative. Just be consistent for sanity.

Anything 14 Gauge or better will be fine at 25ft. If you're splitting the 50ft among 4-6 speakers and the front speakers are close - say 5-10ft, 18 gauge would be fine. If you have long runs with high power (generally front speakers) then you need heavier gauge wire like that Monster, otherwise it's just profit dressing for the dealer.

Edit: I might be assuming too much about the "home theatre system". If it's a big system my ballpark gauges wouldn't be adequate. We really need the amplifier output specs and wire lengths to each speaker before giving accurate advice.

Oh, and wire left/right pairs with the same lengths, even if it means coiling extra on the floor.

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