phillips sound labs ???

i have a phillips sound labs amp it has a550 written on it and it is quite a large amp. its bigger than my rockford501d, but this amp seems alot weeker than 550 wrms briged at 4 ohms.
Any guess on what the wattage is briged at 4ohm??
iam tring to set the gain on this amp and have no clue of what voltage to set it at,because i dont know the wattage.
my guess is 300wrms briged@4 hard to tell ive got wired to an svc4ohm alpine swe1041, 200wrms ,600peak and at 3/4 of gain on amp and headunit the sub is pounding like crazy and still sounds good its probally getting too much wattage right?