Changes to older system

My system is the following, electronics and speakers bought from the store where I worked through college and grad school in the late 80s and early 90s:

- Cambridge Audio CXN v1

- NAD 1600 preamp

- NAD 2200PE amp

- B&W Matrix 3 Series 2 speakers 

- Monster Cable interconnects and speaker cable

Overall I still enjoy the sound, but I’ve always thought it was bright and bass shy.

Where should I start to upgrade this rig?

- First and most obvious choice is cabling, but what?

- Second, Quirk Audio can upgrade the amp and preamp, but is it better to do that or buy new?

I’d like to stay in the $2k range per component - used or new.