Here is why you need to be careful with the outboard speakers. The installed speaker in the photos is the factory one. As you can see, the back plane of the factory speaker magnet is already almost to where the transformer is. So if it was deeper, that will be a problem. Unfortunately, most "beefy" speakers capable of enormous bass needs to be deep to have high xmax rating. Fortunately, the outboard speakers don't need to be bass kings, rather it's better for those to behave more like mid-bass anyhow. Fortunately again, the center most "super-bass" speakers don't have this clearance issue. Just understand that the GF-777 case is not very thick and huge/heavy speakers means this sharp is no longer a shippable candidate. Also try not to toss the speaker braces.