I run all three of your options in my frag tank I have the nano streams and in my display I run two VorTechs and one Tunze 6100. Like others said they all have their advantages and disadvantages. NanoStreams you cant dial in the flow rate but they are really small and pointable which is always nice. The VorTechs the technology is awesome, they are quite, dont add any heat to the water, you can dial in the flow you want, and they dont take up much space in the tank downside they are pricey and you cant really point them (although with how broad the flow is you dont have many deadspots). The 6100 is on a single controller which is great being able to pulse the flow, you can direct them but they are a little bulky and once you add in a controller and possibly the light cell are somewhat pricey as well (although I know that when the wireless controller comes out for the VorTechs I will be getting that which wont be light on the wallet either). None the less in my mind you cant go wrong with any of your choices benefit for your setup is that with the NanoStreams in opposite corners they can "fight" each other, if you go with the Tunze 6000 I would suggest geting a single controller which would be good to get the pulsing action, the Vortech with such a broad flow you definitely wont have any deadspots in the tank and when the controller comes out you will be able to do the same things as you can with Tunzes plus the batter backup is nice if you were to loose power so you still had some flow in the tank. All and all I guess I didnt help you get to a decision but this is what I have experiences with running all of them.
