Whelen doesn't strike me as a "long range" type of setup, more of a 300yd slam 'em good style in my mind. I don't see a need to go over 10X with it.
But, Zeiss or Swaro or S&B or a Leupold 2.5-10 is a nice scope for it.
You'l have to decide as to the type of hunting you usually do as to whether or not you want a 40.44 or 50 objective on it though, the 50 isn't real nice for packing around, but is real nice for dawn/dusk low light.
I just picked up a 3-9x40 w/z600 Zeiss to put on a Merkel K1 in 7mag, it's good enough for the areas I will use the rifle in, and small enough to be comfortable to carry in hand. And I put a Zeiss 4.5-14x44 w/z800 on a Win 1885 in 300H&H as it can be used as a longer range gun for hunting and targets. My ,338 WM has worn a 3-9x40 leupold for 22 years.