I have no problem with Gamma Card in my T-Rex & Fun Card in my Diablo Light v2 Rev3.9 in my Topfield TF4000PVR.
But it all depends on the receiver and the CAMs some combinations can get very hot and lead to freezing and damage the card.
But even thou I sometimes use mine as described above, you can only watch one channel at once, I certainly wouldn't advise spending more money just for a better random flicking/zaping of channels option.
Edit: eg. (for me in Topfield TF4000PVR) even thou the Dragon/T-Rex CAMs (and even to some extent the newer Diablo Light v2 Rev3.9) are fairly good at staying cool together and not overheating, the T-Rex/Dragon with Season Interface runs a little hotter, and the Diablo Light v1 Rev2.3 (2.2 version upgraded to 2.3) runs too hot to have any other CAM inserted with it , sitting a fan in front of the CAMs or modifying your receiver with a extra internal fan near the CAMs is also a better option than spending more on a new twin card reader.
