In case anyone's wondering about when meteorite staff can finally be replaced... I wasted a bunch of mats on getting crystal staff to +5 (which is when it hits S-scaling) and even when looking at the upgrade to +6 it is still 9 points behind at 56 int. 224 vs. meteorite's 233. So as far as I can tell the only staff in the game worth putting any upgrades into at all is the Carian Regal Staff. Reason being, somber [7] does not appear to exist outside late-game zones even though [8] and [9] can be found much earlier, so realistically +6 is as high as you're going to get for a really long time -- long enough that you'll very likely have 60 int for the regal which you'll want to take to +9 immediately.
Even Lusat's isn't worth upgrading since you can just put it in a slot you never use and get the damage bonus (and FP cost increase, unfortunately), just like all the other ones with passives. I wouldn't recommend that anyway, it's a massive increase in FP cost for a pretty small damage increase.
I didn't test Demi-Human, it's possible that it could be better since you can easily get normal weapons to +12, maybe even into the 16-18 range if you don't have anything else to spend normal smithing stones on at that point in the game. Not going to waste that many runes finding out when I'm only a few int away from using the regal.