Quadrant...first, what part of the usa are you in...or if you chose to remain mysterious, what quadrant?
Miles is a genius...far too good for us all here! I can rarely understand him, but when I do, it almost always makes sense! lol
Can we go back a bit. You have a vibration, got the tire balanced, and now you're replacing the entire front end.
First, you could just move your front wheels to the back. Balancing guys, nothing personal, aren't always the sharpest pencil in the box.
Also, you can have a bent/flatspotted wheel/tire, that would balance, but which you'd still feel. One clue is a lot of weight on the wheel...but also, spin the wheel slowly and look for a hop in the rim, especially the inside rim. If you notice anything, move the wheel to the back.
If the tires have been in that corner a long time, technically you should keep the tire in that corner, but as tires also sometimes just go bad (internal damage/belt slipping/etc) for the test, move the wheel/tire together...
If they've been in that corner for a while, move both wheels back to the rear, especially if you notice a flat spot on the rim.
Start there. Wheel/tire issues seem to often have a speed range in which the vibration is worst...you drive into that range and then out of it. Also, if this was an 'all of a sudden' vibration you picked up...think wheel/tire even more.
CABs (ca bushings) are fluid filled if OE. This fluid tastes horrible, but it's a great cushion for not only you, but your car. They do fail far before CAs most of the time...but many here think CAs are disposable items like oil and replace them at the first sign of anything.
I don't know when mine were replaced last, but I've had them on for at least 87K miles...they're just getting on my radar list.
Without beating you up on this...there won't be a huge cost savings to do front and rear suspension at the same time...some, depending on the shop, but not much. There are a 1,000 items leading to shaking...well, many of them!
Ok, so sorry, I just reread your post and I think that maybe it is CABs, but checking the wheels yourself is easy and free anyway!
You can diy endlinks and many do CABs too...just saying. Tons of savings!
Go OE...do not get poly bushings...just don't...as Miles said. You can read here and watch vids all over to help you confirm diagnosis of stuff. Have someone stop the car while you watch from the outside. Do you see the wheel rock back at all? CABs
There are wiggling tests too...try them. Use channel locks (big ones) on each ball joint. Inspect the rubber boots...if ripped, grease came out, ball joint would wear out.
You'll have enough things coming up that you'll need to spend money and time on, so I'd just encourage you to move cautiously and conservatively. As far as 'picking low hanging fruit' chose wisely...it's a BMW and lots of the parts...most of them...are probably fine. There are 'weak spots' no doubt, but they vary greatly based on the owners and how they maintain and drive the car.
Great advice you've gotten here...expect for those who said something I disagree with!
I'm so depressed. No one wants to come see me. :(
Mangofy your E46!