Just ran 0.9.3 and the sound volume is perfect for me now!
Both Goonies and 7 new Conan levels sound like great ideas! I would probably vote for Goonies first. If you check Lemon64 ratings, most people gave Goonies a higher rating compared to Conan. So Goonies is the more popular choice if your on the fence about what to do next.
For your Conan idea, it would be nice to have the option to play just the 7 original levels or another option to play your new expanded/enhanced version with all 14 levels together! Or your new 7 levels might be a whole different story separate from the one we have now. Just some ideas.