It is not an issue for most of games, however there are some games like OP's game that are heavily dependend on the big amount of sounds which are unique per layout. In such case the good approach would be to preload only common sounds at start of the project and then preload those unique sounds at the beginning of the particular layout. Once the layout (stage) is over and those sounds are no longer needed, their buffer should be released.
And so I've added several actions to unload/release sounds:
All I'm doing here is just dropping a reference in audioBuffers array. It obviously doesn't work instantly as it's impossible to call the Garbage Collector manually in JS, but it is good enough as GC comes soon during next layout gameplay. In the end the game consumes much less memory with this approach and C2 is no longer limited to light sound dependent games.
Just disabling sounds preload on start is not enough as during the game more and more sounds get loaded into the memory anyway what in the end has the same effect - memory limit reached.
As mentioned earlier, we are still testing those features but it looks promising. 
TheRealDannyyy will write a bit more about it soon. I really hope you 
Ashley will have few minutes to take a look at the code and consider adding those features to the official Audio plugin as maintaining both plugins which are in 90% the same from the code perspective is pointless and it will be easier/less confusing for C2 users.