Brakes: Front & Rear necessary at once?
 

I have an '02 A4 Quattro 3.0 6 spd with approx 145k miles.

The rear left caliper came loose going down the freeway and dropped the pads on the road. I'm going to replace the caliper and do a caliper kit on the right side along with pads and plain Zimmerman rotors. I was thinking of Hawk HPS or EBC Red Stuff pads and am leaning toward the Hawks.

The front pads look to have plenty of pad left. The rotors, front and rear, are fairly smooth.

I'm an Audi newbie, love my car and want to have it in good order but don't want to spend unrequired $$$ right now if I don't really need to and if it's not going to cost me more later.

What should I be aware of and do I chance causing myself unnecessary grief if I change rear pads and rotors without changing out the front at the same time?

Thanks for your feedback.