What meg-ohm input resistance does one need to measure 1% resistors? What does the tolerance need to be of the multi tester? Bob, a novice with basic electronics.

I'm looking for suggestions for headphones and a DIY headphone amp. I'd like to use my turntable, with my BAT VK-P10 and BAT VK-50SE. Unfortunately, I need to ware a hearing aide in my right ear. My right ear is around 18db lower than my left. Ideally, the headphone would go to a...