Have you considered tuning the gun you have? Maybe even changing it to .22? You can mod the trigger to be day and night better, and a tune will usually net you about 25% more power, but it varies from gun to gun. I can show you how to do the trigger and a full tune for a couple bucks if you have some tools.
Changing to .22 is about $21 to $30 depending on how you go about it or if you want to install a suppressed barrel. I almost always go suppressed when I change the barrel, and always with .22.
If you're worried about .177 going thru game you can try H&N Crow Magnum pellets, they're one of only a few hollow points that actually work.
Going with .22 is good too, but they're slower with more drop. A tuned Optimus will shoot a standard weight .22 pellet at about 750+. In .177 1000+.
If you buy a nitro gun or convert your gun to nitro you will gain a small amount of power, but only if you tune it as well. Nitro are harder to cock, more expensive, and have a much higher failure rate than coil springs. They're quieter in an unmodified gun, but when properly tuned a coil gun can be as smooth and quiet.
If you want more power, like a magnum then the RWS 350 is hard to beat. Low cocking effort and weight for a magnum, better than average quality, but expensive.
The Trail XL is nice because it is very quiet, but cocking effort and weight are more, also expensive.
The Ruger Air Mag is an RWS 350 Clone, but a poor one imo. They are the cheapest magnums out there, but also the lowest quality imo. I would never trust one to work right without taking it apart first for an inspection.
The Stoeger X50 is like a no frills Trail XL, cheaper than the XL, but still overpriced imo.
I'd seriously consider tuning yours first before deciding on another, but it's up to you. Just throwing some options out there...