I'm interested in any simple mod that can improve performance
Before you shell out for go fast bits, have you serviced the car and checked everything else is functioning okay? Things like throttle body and so on - simple but important stuff. If the car is in good service condition and you still feel its lacking in power then go for it, install the HM's and full exhaust.

I had the opportunity to drive my AWD with a few different exhaust combinations, pretty much trying everything in several different combinations. I'm now running HM headers, sports cat and a custom 2.5" cat back, but the HM's are the key item, not just for perceived power but for eliminating the drone. If you're AWD is not a sports variant then a rear muffler may help also.