A 25 amp fuse might be too small depending on the specific amp.
You say the amp is rated at 300x2 and only has a 25 amp fuse. Well, my amps are both rated at 75x4 or 300x2 and the manufacturer spec is for fusing of 120 amps for each. Now mine is a hog of a class AB amp that draws a lot of current (but it sounds wonderful!!

), and if your amp is class D that could explain the lower fuse rating. But still, 25 amps is a little small I would think, especially if you're laying into it very much when the fuse blows.
Find the manufacturer's website and see if they have that kind of technical information on it.