If you use good 8 Ohm speakers (no nasty impedance dips) then regular wire is probably still Ok for surrounds. If you use the all too common 4 ohm variety speaker (it may say 8 Ohm on the box but is it really 8 Ohm?) then you'd best go with some heavy thick wires for such a long run. In either case heavy gauge wires will not do any harm.
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there are a lot of articles on this on the web- first, 4 0hm or 8 ohm matters as stated above--in general 14 gauge or better for that length - can't go wrong with thicker-i have a 40- 60 ft run with 4 ohm-- i ordered 10 gauge at first but it had to go under the carpet( not ideal) and was too thick and inflexible so i switched to 12 gauge and its perfectly fine.
Here is a link that contains a table of resistance per unit length (ohms/kilofoot) for the different wire gauges:
You will see that 14 gauge is about 2.5 ohms per kilofoot, which would be about 0.2 ohms for the 80 foot two-way path that you are dealing with. That seems reasonably low in relation to an 8 ohm speaker, especially in a surround application. If the speakers have significantly lower impedance and/or good bass extension, a heavier gauge may be desirable, as the others have noted. The table may help to give you a feel for how much each increase in gauge will provide in terms of lowered resistance.