Welcome to the forum! IIRC there are a couple of apps that claim to be able to boost the iPad's volume but I don't think they have very good reviews.
The bottom line is that the speakers are the weak point. They just aren't designed for loud sounds and I suspect any sort of increase in output would just cause them to clip the audio.
There's this odd little device called a "SoundJaw" that actually helps direct the iPad's sound that might be of interest. It was a Kickstarter project, but I think it's available now:
However the best bet is to probably get an external speaker or speakers. There's everything from a little speaker that clips onto the iPad by connecting it to the audio jack to docks to full-on stereo setups built especially for the iPad. A quick Google search will give you some ideas.
Of course you can always use headphones. I have a nice set of Zagg headphone/buds that sound terrific.
If you really want good sound you can use AirPlay to send your iPad's audio to a "real" audio system.
Hope that helps...others may have some suggestions.
