To those of you who have more experience trading with ARCA...let me give a hypothetical trading scenario. Let's say I want to buy 1000 shares, and at the inside ask there are a total of 1000 shares available through various ECNs (but no market makers) I realize that if I place a trade through each ECN, the trades will go through instantaneously, but it will take me several seconds to enter all those orders. If I just use ARCA, how quickly will that order go through? Am I losing milliseconds? Seconds? Remember, I'm assuming no market makers to preference. I'm also assuming that I'm the first one to take the offer.