Thanks Demi, I ended up going with
Kingston ValueRAM 16GB 1333MHz DDR3 PC3-10666 ECC Reg CL9 DIMM DR x4 Server Memory model no.
KVR13R9D4/16
I got them for between 137 and 144 a stick from both Amazon and NewEgg.
This memory works great in a 2010 Mac Pro (5,1). I usually buy from OWC but this was so much cheaper I wanted to take a chance. So a quick review, this has everything you would hope.
First, it has temperature sensors that show up in OS X if you use tool like iStat menus.
Second, it runs much cooler than the 8GB sticks I used from OWC (these run at about 125F, while OWC ran at about 150F). It ran cooler despite the OWC being lower capacity and it having the fancy heat sink things on the memory.
Third, you can run 4 of these per processor bank and it will still run at 1333MHz and not drop down in speed to 1066 like many other chips will!!! That is amazing because it basically is running better/faster than Apple said was possible.
(i.e., apple recommends you load only 3 sticks per processor bank to keep everything running at 1333MHz, and if you use the 4 slot you can expect a drop down in speed to 1066MHz, but this will run flat out so you can max memory to 128GB (with yosemite) and experience no speed decrease--I believe the latest OWC memory also lets you do this). Once I discerned you could run at full speed even using 4 slots, I decided to load up and max memory out at 128GB)
I also ran memtest 4.23 on this, and it passed with flying colors (it takes about 4.5 hours per 48GB for a single pass of memtest so be prepared 12+hours of testing if you load up the full 128GB using these sticks).
I got 3 of these for $137 per stick on amazon, but the price went up to 160 something right after I bought it and now dropped down to 144. So the prices vary wildly and daily on this. So I bought 3 sticks on amazon and then another 6 sticks at newegg as it was cheaper (particularly without the tax hit).
Best bet for finding the best price is just do a search on google shopping for the model number: KVR13R9D4/16.
Hope this helps some others that are on the fence.