This is an opinion question so you will get some variety. I shot a German clamshell 9.3x74 double which was quite unpleasant to shoot as it was under 7 pounds (don't know the exact weight). It had a small scope at that. I prefer as light a weight as possible but would estimate the scoped gun should be in the 8+ pound area for most people. 9+ is way too much for a 9.3 x 74. My 470 is 9 1/2 pounds and comfortable. The 9.3 x 74 is about 200fps under a 375 so you might judge from that is you have shot those.

There is a rule of thumb from the 19th Century for shotguns. That being ideal weight should be about 96:1 of weight of gun in ounces to weight of projectile in oz. That means a 6 pound gun is about ideal for a 1 oz load and a 7 1/2 pound gun is about ideal for 1 1/4 oz loads. This is with non-autoloaders and hard pads with velocity about 1150 fps as per the old times. It does not translate too directly to rifles as higher velocities are felt more viciously than simply comparing total energy. Bottom line is that it is a personal thing and experience is the best teacher.