Not getting gigabit on gigablast

I just signed up for gigablast, and I have a suspicion that the signal to my modem (Motorola SB8200) is not great. I've done multiple speed tests that are inconsistent and usually around 500-600 Mbps (going from modem straight to laptop). I've tested both with the Cox speed test and dslreports. Additionally, I have T3 timeouts and Dynamic Range Window violations in my modem logs. I've also seen random reboots in my modem logs. Should I have a tech check out my signal?