Vibration in steeling wheel at mid-high speeds, and while turning

Need help understanding why my 2008 Subaru outback seems to be
vibrating from the front end (I believe). I just replaced all 4 tires and had an
alignment, so I know those are not the issue. Vibration seems to be coming
from my steering wheel and the front end in general. The vibrations get
louder and faster as I gain speed, but turning the wheel even slightly makes
it much worse and much louder. At a certain point (~80mph) the vibration
seems to either die down slightly, or at least not get any worse (until I turn
the wheel). Could it be bad wheel bearings? Or is something wrong with my
axle? The vibration has gotten worse over time and I thought it was a mixture
of old out of balance tires, and a misalignment, but neither of those has done
anything to correct the issue. Thanks in advance for the help.