Am I being fair?

Recently I posted a add on Audiogon for a VAC amplifier, in the add I stated "preference given to local buyer", the amp is heavy and it's stressful sending gear across the US, even when it's insured. What happened, the first day of posting the add, I had many reposes, and a local gentleman was #10 of the people who were interested in the amp, he stopped by my house and bought it right away. When I informed some of the other e-mailers to the add, the amp was sold, some were upset, saying I should sell to the first person who contacted me. I never made any commitments to selling the amp to any of the e-mailers. Couple of the people are threatening to give me a negative feedback. Should we sell to the first person who responds to the add? Just wanted a opinion from other member if they have come across this situation also, thanks.