Humm, sounds like you may want to have a look at the passport PAs !

The Gains should act as volume controls and if they are not cutting it, either I) the amp is bust or II) the amp is not bust and is just not loud enough.

A 60 w amp should blow the balls of a 12 w guitar amp and give you more than enough volume to play parties etc so you might want to consider having a friend who knows about amps / service guy have a look at it. Id get a quote before having any work done as it may cost more to fix than to get a new one !