For low-light stage work, a 70-300mm f/4.5-5.6 is generally not ideal. At those apertures, it’s relatively slow, so you’ll often struggle to keep shutter speeds high enough for performers in dim light.

The main tradeoff is simple: long, fast, and cheap rarely come together. If you want 300mm with a fast aperture, it gets expensive quickly; on a budget, about f/4 is usually the best you can hope for, while f/2.8 telephotos are typically much pricier.

A better budget-minded approach is often to use a faster prime and either frame wider or crop later. Based on the suggestions given, the Nikon 85mm f/1.8 or 105mm f/2 offers a much better balance of speed and usable reach for stage photography than the 70-300mm zoom.

So if low light is your priority, choose aperture speed over maximum zoom range.