Re: can i do this?
You could, but I don't recommend it. AMD chips will run pretty cool from those two families anyway, but the Regor chip is a 45 watt chip, while the Heka (Phenom II X3) is a 95 watt part.
If you try it and get really high idle temps (50+) then I'd just suck it up and buy a cheap tower heatsink if you can. I'm a big fan of the Freezer 64 Pro, I use it currently on a Phenom II 940 BE and it does fine, though there are other great tower heatsinks out as well.