Shaking Steering Wheel
 

I drive a 2007 Mazda 3 GT Automatic 5-door. 65k miles
The car was a cheaper buy and this problem just started showing up so I know why, but that's besides the point. The steering wheel shakes between 40-60 very noticeably, and as the speed increases it doesn't shake as much, but never stops.
I've had a new alignment done, tires balanced and even replaced the front struts as they were giving me issues, yet this still remains. I did not do the back right away, as I assumed since the front tires do the turning that would fix this problem if it was causing it, they will be changed soon.
Anything I may be overlooking or should check? I just do not want to go spending tons of cash on different assorted parts if someone has experienced the same and knows what could be causing it.

Thanks

Have your tires checked for separating belts. It's weird and will drive you crazy, but the tires are probably the problem. Have them checked at a real, reputable tire dealer.

the alignment shop should have checked all the joints, but a loose / worn ball joint or a tie rod end could allow the tires to shake. Does it change when you turn side to side, change lanes?
Possibly the lower control arm bushings or something. You can eyeball the tires & look for patterns or bald areas. That would point to which tire is causing problems, if it's a seperation or broken cord you may be able to see that in the wear pattern too.