Bought an '08 GXP last October, used with 20K miles(Carfax said one owner, NOT a rental car haha!) Haven't even had car a year and seem to be having serious brake issues. Very slight tremble when beginning to brake, when at complete stop and then beginning to accelerate-there is a "knock" or "clap" sound, hard to describe but almost feels like brake or something else is stuck and is unsticking itself , loud squeaks, squeals at stopping - any speed... have googled a little bit but seem to be many different answers, from changing GM parts to aftermarket, to trying ceramic brake pads, driver wear & tear, caliper torque wrong, etc.
Took car to tire place back when noise started. Manager is very good friend of mine and pretty sure he wouldn't try anything shady. Manager said pads were still fair, would be a waste to change them at that point. Said noise was most likely b/c car needs to use ceramic pads due to the performance brakes(drilled and slotted, as I'm sure y'all know), and car does not currently have ceramic pads installed. Rotors were OK but would be affected as cheap pads started to wear down more. Also quoted a price on ceramic pads, can't remember exact amount but were def pricey compared to replacing pads on previous cars...
So my question is - any of y'all familiar with this issue? Do you suggest forking over for the ceramic pads or will that fix the problem? Should I try aftermarket pads(rotors if needed) or take car to dealership for GM parts? I have recently replaced both front tires, possibly need an alignment(maybe that's the slight shaking)...
Please forgive me if this has been posted previously somewhere else! I'm a newbie. Always loved this car - love the FWD and although I don't drive it hard 24/7 it can definitely handle when I am in the mood to scoot around! Hubby drives '08 Impala SS(cousin to the GXP, as I call it ), and he likes my car better than his!
Thanks in advance for help!!!

Ceramic pads are not that expensive. Orileys sells their own brand ($52) and Wagner Thermoquiet ceramics are under $60. I also have a wife that has front brake issues constantly. She drives pretty hard and must get on the binders alot to make yellow lights. I'm not saying this is you, but most ladies I know who drive performance cars do drive this way. After that hard stop, they sit with their foot on the brake for 2-3 minutes while the light is red. This super heats that part of the rotor which car warp them or cause a glazed spot which will not grab as well. I tell her if she does panic stop, once there is a car behind her, roll slightly forward and put the car in N, than use the brake just enough so you don't roll.
If it was my car, I would replace the pads with quality ceramic pads and take a sander to the face of the rotors to break and glazing so they seat with the new pads. After new pads, you MUST drive like gramdma for a few days to break them in, or you will have issues soon again. While the rotors are off, check them for warping. If warped, order new E-line spec Drilled and slotted rotors from R1concepts.com

i say relpace rotors and rebild calipers sounds like a pad is gettin stuck get the best pads you can and make sure u grease up fittings if still problems replace calipers