Originally Posted by VehiGAZ
Whoa doggies - let's start with the simplest and most likely culprit - tire balance.
A vibration that occurs only at certain speed ranges is generally one of two things - tire balance or a bad CV joint (not an alignment problem). If you feel the vibe in the wheel, it's one of the front tires; if you feel it in the frame (i.e., through your butt), it is probably one of the back tires.
Since you said the tires are new, I suspect them the most. Have them rebalanced by whoever put them on and if that doesn't help, have the CV joints checked out next.
Granted, your alignment may be messed up, but that's probably not the cause the vibration. It may have caused a CV joint to fail, though, or so I have heard.
Good luck!