You can leave the fan off the RAM. You don't actually need to provide much cooling for the RAM itself.
That said, the Dominator sticks, in addition to being massively overpriced, are absolutely huge. If you've got the 3x4 GB kit, you'd do better to move them into the second group of slots. That would give you enough room to install just about any HSF. I'd suggest the Scythe Mugen 2 Rev. B
, as it can't be beat in terms of value.
If you've got the 6x2 GB kit, you're in a bit more trouble. You'll need to make do with smaller coolers that don't hang over the RAM slots. I think the Coolermaster Hyper 212 Plus
should fit the bill.