Poor Bass Output?

Hi, I have a question regarding my sub/amp combination. I have a MTX Thunder 801D Amplifier, which is rated 600Wx1 @ 2ohms (Birth Sheet), 12v, and I have a new RF T110D4, which is rated 600WRMS. My problem is, I can not get the sub to sound loud at all. Its very minor in the way that the bass is coming out. I have a friend with the same sub, and his is louder than hell. The sub is wired correctly, and everything seems to be in order. The only thing that I can think of is that I am running 4guage to a distro block, and splitting it into 2 8guage wires for the power for this amp, and the mid/tweet amp. Would not having 4guage directly to the sub amp cut the power this dramatically? The sub moves lots, just doesnt go "loud"... Ive tried new grounding area's, and every adjustment to the HU, and amp that I can think of. The amp gets hot very quick, and the louder I turn the volume the crappier the bass becomes. Please help, ive spend a whack of cash on this stuff, and its just not doing what it should. Chris.

Box, box, box sounds like the issue here and maybe just maybe the voice coils are wired out of phase. Disconnect one voice coil and play it again and see how it sounds.Top Secret, I can tell you but then my wife will kill me.

i was gonna say the same thing as rob, im guessing on one of those two things.double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer