I looked at the rear control arm bushing through the hole with a light, and really I must say it looks 100% intact, I could not move the arm but then again much couterpressure from spring... but again really it does look 100% intact - I am assuming it's ok.

Given your description I'd still suspect the control arm bushings. When you go over a bump there is a lot more force delivered to the A-arm than you can begin to duplicate with the car jacked up. And a visual check won't always tell you what you need to know. Did you tighten the bolts at the control arm? Also tighten the crossmember bolts, and the end link grommet bolts. Tighten up everything you can see on the suspension. If none of that gets rid of the clunk, swap out the control arm bushings and report back the results.