AMEX has little volume for a reason.
I make my living trading nyse stocks, but in 2002 I spent some time trading AMEX stocks, primarily SPY. I found it to be an unfair and abusive system. Cancels are not made until the specialist is sure that he cannot find an edge in filling your order (i.e., if the market moves against you, etc)...literally minutes can go by not knowing if you've been filled order not. Limit orders don't have be filled at the best bid or ask. For example, I once had a 1000 share buy order for SPY 0.10 under the bid, the market started to turn down, so I cancel...the order remained open for almost a minute until SPY was trading at 0.50 under my limit price, then I was filled AT my limit price--instant $500 loss...SPY has great liquidity and could have easily filled me at the current market price.
I've experienced every abuse from NYSE specialists, but I would rather trade with the worst NYSE specialist than the best AMEX.