Yes, Vardars perform quite well.
Take a look at VSG's review of the Vardar F4 (2200 RPM) and how it compares to the Gentle Typhoon AP-45 (2150 RPM)
You'll see that the GTs and Vardars perform similarly in terms of noise to airflow.
Source: ExtremeRigs http://www.xtremerigs.net/2014/12/03/first-look-testing-ekwb-vardar-fans/
This is how the Vardars compare to each other in terms of noise levels if you're curious how the lower RPM versions perform:
Now, take a look at how the lower RPM Vardars perform in comparison to other similarly priced fans currently on the market:
They will be able to push the same amount of air at lower levels than the SP120 QEs. I actually just ordered 16 Vardars to replace all my SP120 QEs maybe 15 minutes ago. You can get them at NCIXUS for $14 a pop before shipping.