I did actually do a bunch of testing with SAS SSD SS530/SS540 with expanders and without with 9300 vs 9500 series, and the 9500 actually came out on top, will see if I can find numbers, sadly when you introduse expanders you loose some umph, and with ZFS even more... at least with expander AND ZFS they are somwhat inline with each otherIf you are planning on adding NVMe JBODs, you have to go 9500. 9400 only doesn NVMe internally. If it's just SAS3 JBOD's, save money and go 9305w-16e.
on other hand, on older hpe systems the P408 actually came out and did better than u.3 and trimode controlleres/enclosures.