Joe Bob outfitters had the Romeo Zero on sale for $150, worth seeing if they've still got any, mine came last week. It worked great in my Hellcat, shot it for the first time today. Its not my favorite red dot design -- need to remove the sight to change the battery, non-click adjustments that need an 0.050 hex wrench. But the small size and light weight overcome these deficiencies for this situation. Another plus is the Romeo Zero sits low enough that you can still use the stock iron sites as a "back up" which also really helps when making zero adjustments.
You will need different screws (or modify the SIG supplied ones) to mount it on your Hellcat.
I found the mid level brightness was fine at the range today on a very bright hot August day.