Gaming
I like gaming, but between already being a member of message boards, subscribing to 4 gaming magazines, web sites like gamespot.com, etc...
I have to say I don't feel a big need for more on gaming, and the question might be finding a niche.
If it's just 'audioholics members talk about games', then that's its own niche.
But it seems like Gene is looking for more or he wouldn't be asking the question.
Things like cheat codes already have reliable web resources, so a hit and miss message board is marginal for that.
The obvious angle is audio/video equipment and games.
For example, I use an Audigy 2 ZS Platinum and Klipsch Ultra 5.1's, and ponder gaming on a home theatre system.
Gaming sites have all kinds of threads about the differences between sound cards, the ideal speakers, and such.
Even threads on games that have the best sound effects might be of interest?
Similarly, there are all kinds of discussions on the best video equipment to use. Things like what monitor frequencies to set, LCD lag etc. are of interest.
One note - there is an issue of seperating platforms. It seems iffy when it's questionable whether there're enough people for a gaming forum, but making a PC gamer read through 80% threads on console topics creates a lot of noise, making the forum one to skip for some.