TradeMaven is not just an order entry system. It has the most comprehensive auction market style charting that I have yet seen. Also, it allows scaling in at multiple prices on the same DOM.
FYI- While I have no financial stake in TM, I do have a relationship with them. The relationship is there because they are responsive, they listen, and the software does what other software can't.
Regarding data feeds, TM offers several options. Transact is not on PATS. Another major retail broker with their own feed is coming soon. And, esignal can be used for r/t sim and chart backfilling.
I am also an IB customer and have used Ninja and was most satisfied with it's operation.