Have the Vortex you are talking about, is pretty good on noise actually. You may not need to get a new fan if you haven't already tried out a few things to reduce noise with your current fan.

Not sure what your grow space is like, but if you can line the wall next to the fan with a blanket, they absorb a shit load of noise.

Another thing that cuts down noise from the fan is insulated ducting. I personally don't have insulated ducting but it's on my to do list.