That A-Data ram is rated at 1.8v, and should be just fine at 1.9 for 850MHz and default timings.
The FSB VTT voltage affects the cpu as well on 45nm cpu's, and many suggest 1.3625 for a max on either. I have read the data sheets as it being a bit higher, but unless you are having a problem I would stay at 1.36 and below.
if you are stable at 445x9 I would just stay there, thats a nice OC and good voltage. If you are unstable just bump the vcore up a bit and try and stablize it.
CPU usually have a spot where it needs a big voltage bump to get to higher OC. Some will be rock stable at say 1.25v and 3.8, but need 1.35 to reach 4.0....