IMO,
way too small heatsinks, and thermal tape is so-so.
edit:
Grab a hacksaw and carve into some surplus heatsinks and you'll end up with something like this:
http://img.techpowerup.org/121021/largon-hd4890-custom-vrm-sink.jpg
The VRM areas on my cards are really narrow and surrounded by capacitors compared to the card you show in the picture; that specific heatsink would really need to be trimmed to fit in the area. I would also need to make sure it fits in a two slot width so it can be used in crossfire, but I'm sure it could be cut. The biggest issue I have with it is that I just don't have many spare parts laying around; I generally sell everything I don't use on eBay. If you have a suggestion where I can buy a heatsink like that for a moderate price, I would appreciate it.
edit: There's also conveniently no screw holes to secure a VRM heatsink to the PCB of my card.
On another note, I determined that the crashes I have had are definitely related to crossfire. Both cards work fine individually when crossfire is disabled. And when crossfire is enabled, I get lots of rendering errors and occasional crashes. So I guess that crossfire in Windows 8 is broken. I hope that newer drivers fix this.