Just use similar specifications as HK-47 or an HK-50...
In any event, if Revan can force Xizor into having to play this as a military campaign, Revan will win.
If Xizor can force this into an underworld style situation, he has the advantage.
Then he might just wanna go with an HK-50, there is literally no difference between HK-47 and HK-50. The only notable difference between the two units, is that 47 has a different personality and a long history, and HK-50 having a different armor color scheme....aside from that fact, I haven't seen anything that shows them being different...in terms of being an assassin droid and killing their targets, even if there is a difference between 47 and 50 its probably not that big of a gap.