Why you looking for tall heatsinks ? Be aware that these tall heatsinks are a "style" remnant of the ole days when these tall heatsinks actually served a function. Today's RAM doesn't need the extra cooling and, testing shows that removing them can actually improve performance in some cases. I'd stick w/ low profile RAM and, if ya have the budget to pay more for RAM, invest the extra moola in lower CAS settings.
If it's a "stylistic" choice, as one function the tall heat sinks do serve is they "look cool", and ya stuck on the Vengeance, then I'd look at the Prolimatech Genesis or the self contained air coolers. The Antec 620 / 920 toast the equivalent models from Corsair. The 920 betas the H70 by 4.7C (both quite noisy) and the 620 beats the H50 by 7.2C and is actually very quiet. Be aware that they can be problematic in MoBos w/ 3 or more PCI-E slots (radiator hits top GFX card).
http://benchmarkreviews.com/index.php?option=com_content&task=view&id=721&Itemid=62&limit=1&limitstart=5
http://benchmarkreviews.com/index.php?option=com_content&task=view&id=694&Itemid=62&limit=1&limitstart=4
On a side note be aware that the Asrock Z68 only provides a paltry 1 year warranty compared with the industry standard 3 years offered by Asus, Gigabyte, MSI, etc on their Z68 boards.