There is no question as to who provides the best rate/technology for scalpers. It would be a combination (of which there are several) of a DAT broker offering a penny (or less) per share commission structure using a platform like the Watcher or one of several platforms designed in similar fashion. Examples would be: Broadway trading-though I believe they may be prop only Sonic Trading Point Direx (for whom I currently trade) TradeScape (the "Professional" version of their software) Brokers using trading platforms built upon this similar technology would include: Sonic Trading NobleTrading F1Trading www.pointdirex.com tradescape and others I am sure............ Finally, I think that the SL4 software has some very interesting claims and apparent features that look intriguing. Let's all do our due diligence and perhaps they should be added to (the top) of this list!!