I would be careful if I were either of you.....here's why:
He could send you the check....and you could agree to hold it....he could get the amp, and when he is installing it, short it out or fry it completely.....he stops payment on the check and sends you back your chunk of aluminum.....your pissed off.
or
He could send you the check....you cash it as soon as you get it...( it's either good or it's not, he can't stop payment on it and then reverse that) (or he can't say the check isn't good until he deposits money to cover it, why would you accept a check like that?) anyway, you cash it when you get it, he gets the amp, he isn't happy with it, he tries to stop payment, it's already been cashed......he's pissed off then.
The only way around this is to use a third party to both verify the condition and quality of the amp and to verify that the funds are good because they are made payable to the third party and the money will have been collected. There are a couple of online services for that or you can use a good reference for the both of you, someone who is unbiased and fair.
Just thought I would point out the possibilities....I hate to see people get screwed over. That is why I do so much business on
Ebay and my feedback is over 645+.
Peace...(yeah, right!)