well there are an almost infante amount of Mem opions. Memory w/ Samsun TCCD IC's works well w/ a64, they are very versital, and get usually between 250-280mhz, and some even see above 300. at 280mhz i have seen then as tight as 2.5-3-3-x. these are avalible on many new 2-2-2-5 rated memories. The best so far seems to be PQI's PC3200 Turbo 2-2-2-5-1T. Or adatas DDR566.
Also memory w/ micron IC's work well. there are two revisions ATM. one is mT-5bc, and mT-5bG. the -5bC's are avalible on OCZ EB memories, and usually end up w/ 250-270 w/ 3-2-2-x/3-3-2-x. these tend to run hot, even at lower Vdimms(ie 2.9) and i would suggest using a fan w/ them. The -5bg's are avalible on Crucial Balistics pc3200 and work well. usually get slightly tigher timings that the C revision, but ATM the OC of them is slightly inconstistant.
Also if you have/ can get it, bh-5/6 is still a good option, if you arnt afraid on high Vdimm and 3.3v rails. because on this board, to run above 3.2vdimm you will need a hight 3.3v rail(ATM my vdimm is at about 3.55-3.6v, and my 3.3v rail is about 3.74v
)
and as well Hynix d5 or d43 work ok to, there usually much looser in there timings that the above memories(3-4-4-8, is the norm) but are more readly avaible, and usually do 250-280.
the choice is yours