22 gauge will work!
Furthermore, my cable runs are no more than 25 feet which should be fine if I double the 22 AWG wires (effectively 19 AWG) for an 8 ohm load (right???). Plus I'm hoping since the cable is twisted and shielded that I will have a good clean signal even with the smaller wire.
As much As I harp on people using too big of wire you are actually close to using too small of a wire. If you are running speaker wire through a wall always over-spec it!. You may be only running 80watts now but in the future you will likely upgrade to higher wattage.
Basically this is what you have:
Total Resistance
Wire Gauge Resistance /Ft. 5ft 10ft 25ft 50ft
4 0.000292 0.00146 0.00292 0.0073 0.0146
6 0.000465 0.002325 0.00465 0.011625 0.02325
8 0.000739 0.003695 0.00739 0.018475 0.03695
10 0.00118 0.0059 0.0118 0.0295 0.059
12 0.00187 0.00935 0.0187 0.04675 0.0935
14 0.00297 0.01485 0.0297 0.07425 0.1485
16 0.00473 0.02365 0.0473 0.11825 0.2365
18 0.00751 0.03755 0.0751 0.18775 0.3755
20.........0.0119.... 0.0595....0.119..... 0.2975....0.595
22..........0.019.....0.095..... 0.19.......0.475..... 0.95
24 0.0302 0.151 0.302 0.755 1.51
So for 25Ft the resistance of 22 gauge is 0.475 ohms which is 0.475/(0.475+8) = 5.6% You should be okay with 22 gauge.
If you use two 22 gauge wires RT =( 1/((1/r1)+(1/r2)) = .2375 ohms =between 18 and 20 gauge or ~ 19 gauge as specificied before. Then your percentage drops to .2375/(.2375+8) = 2.88% of power on the wire.
Remember though at 80watts 5.6% of your power is absorbed in the wire or 4.48 watts. This amount shouldn't warm the wire too much!