AS5 is not obsolete
http://www.madshrimps.be/?action=getarticle&number=5&artpage=3071&articID=635
http://benchmarkreviews.com/index.php?option=com_content&task=view&id=138&Itemid=1&limit=1&limitstart=3
Are just two reviews that show there is not much difference between ocz freeze, mx-2, tx-2 and AS5. If you factor in margin of error, they can pretty much all be considered at the same level - note one review shows the tx2 better than the mx2, the other mx2 better than tx2,...both show the AS5 in between, margin of error and these are equal, the ozc freeze I have not found enough comparable reviews to say it is truly the best, but it is up there.
The same is true with the Vendetta 2 and the Xigmatek S1283, they are of similar design (The vendetta 2 a knockoff with a few design changes), the included fan spins a bit slower on the vendetta 2,... you will not see a huge difference between the 2 Heatsinks and if you include margin of error in reviews,....
I personally like madshrimps for this one (they have basically the same case as mine so it is a better comparison for me - remember setups can influence cooling effectiveness of a heatsink as well)
http://www.madshrimps.be/?action=getarticle&number=5&artpage=3615&articID=857
It shows the vendetta 2 a whopping .5 degrees cooler when similar fans are used and 1 degree on the following:
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/8580-ocz-vendetta-2-cpu-cooler-review-11.html
However the xigmatek S1283 is usually a good $10+ cheaper (depending on where you go and when) $17 diff on newegg (freeshipping and rebates included), which is more than enough to buy your TIM and a burger!
http://www.newegg.com/Product/Product.aspx?Item=N82E16835233003
http://www.newegg.com/Product/Product.aspx?Item=N82E16835202007
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=10008593