Many thermals in the market now. Keep to 640x480 Resolution. If you "honestly" plan to shoot longer ranges at day or night get a 4x zoom or more. If you are average hunter (+/-150yds) you can get away 2x or 3x zoom.
4x zoom (tight FOV) makes close range location and panning a burden. 2x or 3x zoom makes longer shots tougher but you can digitally (more pixilation) zoom in but location and panning is a lot easier (wide FOV).
If you can do so buy America. But I understand the affordability of cheaper UK, Chinese & Russian made products.