Looking for an ECN broker with a free programmer's API which has decent liquidity for Best Bidder limit order fills. So if I'm Limit Best Bid in something liquid like EUR/USD, I just want to be filled within, say, less than 15 seconds most of the time. Not too much to ask, I hope. Needs to have an API which allows access to the DOM also, in addition to the Order Entry operations. C# or Java. Thanks!