The 6000 RPM delta fan and the Ultra Sleek Vortex 14 are in totally different classes, it won't work. Delta is doing 210+ CFM at max speed, the vortex only 98CFM. There is almost nothing comparable to Delta fans on these things.
There's a fan called the Scythe Ultra Kaze that runs at 3000 RPM, pushes a ton of air and is slightly quieter, but it only works if u have the non-autotune S9 and can downclock the frequency a bit.
YS Tech has fans that can argue with most Deltas, but none to my knowlage that can argue with the FFB series or it's derivatives like the QFR series - the YS Tech lines are designed to be competition for the Delta AFB "low backpressure design" series and it's derivatives.
I'm not aware of anyone else that even gets CLOSE to 200cfm at the kind of backpressure the FFB/QFR/etc lines are designed for in a 120mm format.