Another thought: You have 4 electrolytic caps close to that resistor. It would be good to know how hot it gets in that area. A multimeter with a temperature probe would be useful here. If it were my amp, I'd want those caps are working-life rated at 105degrees - to be on the safe side. Were I building that amp, and that resistor gets hot, I'd either vent the area above that resistor, or mount the resistor top-side (with careful insulation of the leads, so no exposed conductors).
Sheldon
Got it