I just upgraded my base model brakes a couple of weeks ago. I bought calipers from a Q50 from LKQ off of eBay for $607 shipped. Mechanically they were perfect and cosmetically they only had a few small chips on them. I put PosiQuiet ceramic pads from Z1 in them and used rotors from Autozone. You'll also need to either get the shorter banjo bolts from Z1 or got to SS lines. I used the shorter banjo bolts just to save some money for now, $20 compared to $100.
When you put them on you'll need to either trim the dust shields or switch them for the proper shields. I trimmed them because the shields are a pain to get off.
I also spent some extra time before hand to paint the calipers.
