Re: "tactical helmet"
PT Alpha is a good helmet. Many online vendors won't sell any higher level "tac helmets" with ballistic protection to civies.
The PT alpha works well. Depending upon which mount, monocular, it would be a good idea to get or make a counterweight to mount on the rear of the helmet to balance everything on your head.
For the PVS14 Mount, if you can afford it I'd recommend the Wilcox G24 Mount with the Wilcox J-arm it will attach to the Opscore VAS shroud which is an option for the PT Alpha Helmet, if you purchase from Victor at TNVC. It is heads and shoulders above the Norotos USGI "Rhino" mount with the USGI J ARM. The USGI J ARM doesn't lock up 100% solid, the Wilcox does and has easy push button adjustments and quick and accurate swing arm adjustments from Left to Right eye.
With any mount don't forget to purchase a safety lanyard to clip onto your monocular unless you can afford to purchase a new tube or monocular.