Lower Control Arms / Brackets: Do I need them?
 

I'm finishing up buying all the parts for my suspension build. I'm lowering the car with the Steeda Sport Spring 1" in drop in the front, and 1.25" in the rear. I just bought the Koni STR.T, BMR panhard bar, and MM caster/camber plates. Do I need upper / lower control arms or the relocation brackets? I don't want to have additional vibration due to the change in the pinion angle.

You don't need them, I ran a similar setup to you for two years without upgraded upper and lower control arms without any weird vibrations. If you want to upgrade you can always buy the Steeda "lowered" upper control arm and mounting bracket to adjust your pinion angle, or just get an adjustable one and do it yourself. You also don't have to buy the lower control arm relocation brackets. I just have the upgraded Steeda lower arms without the brackets and noticed a huge difference after installation. I used to have issues with heel-toe downshifts, and once I upgraded my upper and lower control arms the car stopped skipping around during the downshift.

Do you have to have them? No. I recently installed the BMR LCA Relo Brackets and used the middle hole to correct the control arm angle. I was not expecting much but the test drive was a pleasant surprise. The car feels more planted. I waited 2 years thinking these were not needed & now wish I had done this mod sooner.

I agree with GAZRNR. I had a similar set up with the stiffer Steeda Boss 302 springs. You don't need anything more for a daily driver car. You will be very happy. In fact your mods waiting for install are a bit of overkill already.
I did add the Steeda lowered car UPA and felt it was beneficial on the track but for street use not really needed.

The MGW shifter is a terrific future mod. I tried other solutions and nothing compares to the precision of the MGW stuff. Transforms the shifting. Seems like a different transmission was installed. I just received the latest Race version and will be upgrading to their even better solution. Also switched to Redline tranny fluid and it helps as well.

Agreed with the posts above. You don't "need" any of those parts, but they improve performance significantly.

These lower control arms, this UCA & Mount, and these LCA Relo brackets work extremely well as a package. They're Made in America, they carry a Lifetime Guarantee, and you get 10% off using code forum15. :)

I had significant wheel hop after installing the Konis and ultralights. I'll be installing control arms and brackets this spring trying to at least reduce, and hopefully eliminate it.