Doesn't really apply to guitar amps unless you plan on running your cab 85 feet away from your amp. At 85 feet, 24 gauge wire (which is quite small), you're only losing 3db. The largest distance I've seen people run their amp from their cabs is probably... maybe... 3-6 feet. If that. And most speaker cabs use 12-16 (maybe 18) gauge wire. So you should be pretty good all the way up to 50-60 feet at least. And if you run your amp at 16 ohms, you can go even farther.