Heyyo,
Yeah, my case also sucks with air circulation man. It's a NZXT Guaridan (cool light show though), and I have a totoal of 9 fans going innt. The main prob with heat seems to be from the PSU and the CPU. Ok, the PSU because it's generic, and only had 1 skinny 80mm fan innit. Needless to say I replaced that little one and put inna fatter 80mm fan and mounted a 2nd fan on the outer side of the psu (heh, I guess I should've cut a hole innit to help the airflow more).
The HSF is a thermaltake volcano12 which I got for free. Because some dumb person tried installing it with force and pliers and then was upset that it wasn't cooling right. The clip is also damaged. Been bent and unbent too much. I tried tightening it, but not 5 mins later does it go back to less bent and the temps stay at 50ºC. With my next system I'm soo replacing it.
That zalman 7000cu HSF solution should work fine. You used thermal paste? another good idea is to sand down the bottom of the heatsink a bit to make it more smooth, this will lower the temps a bit (yeah, even with my broken HSF I get 3ºC cooler than before I sanded it down, so that's always a plus I guess, lol).
The funny part is it Idles around 47ºC and on load only goes up to 50ºC. I've tried putting the fan on full, idle temp stayed the same, and under load was the same... gee.. all that extra power usage just thrown away and it brought noise with it, lol.
So yeah, you might wanna make sure your HSF clip is also pretty tight man. If you had a hard time to hold it down onto the CPU socket? then it should be fine, if it was way too easy? it's probably loose.