Gamo is limited to break barrel and PCPs air rifles which is why I didn't mention them.
Without a doubt, the PCP air rifles are going to be the best in terms of consistent precision and flexibility but they also require some sort of filling option which is going to cost an additional $179 (air pump) - $2,300 (compressor) plus based on your needs. So while you can get a decent PCP air rifle for under $200 these days, you'll still need a way to fill it which adds to the cost. My PCP setup includes $179 air pump, $600 75 cf and $700 100 cf carbon cylinder, and a $2,300 air compressor but most are not going to need all of this.
I've spent as little as $49 for a multipump .177 with a high of $2,300 for a .30 caliber from manufactures that include Crosman, Benjamin, Gamo, Daystate, Air Arms, FX, RWS, Diana, Brocock, Airforce, Extreme Big Bore and Western Big Bore. I also have every power plant except for CO2 and at least one of each of the following calibers .177, .22, .25, .30, .357, .408 and .45 and tested them on a variety of live animals for effectiveness. You can find frequent articles about air rifles for wildlife control purposes in W.C.T. Magazine.