The backplane you have listed is a "TQ" backplane, meaning that it passes SATA connection straight through. It should support SATAII at least, and from what I understand, it should support beyond, as long as it supports the pin configuration.
you can check either on the PCB board itself, or if it has 24 SATA ports on .... well, both sides.
As for the options, Yes and No.
The problem is that finding a PCI-X SAS card. Which boils down to "next to impossible". PCI-X is pretty comparable to PCI-e, but has been depreciated.
The other problem is that the board you've linked only supports two PCI-e cards. you'll be left with 4-8 ports unconnected.
If you replace a card (like with the Dell H200, which is a PCI-e, LSI card, like the IBM ServeRAID), you'll need a SAS expander regardless.
As for replacing the backplane, it really depends on the one that you have. If it's a "TQ" model with SATA ports on both sides, then you don't need to replace it. You'd need a SAS HBA and a SAS Expander card, and a bunch of SAS Breakout cables to hook up all of the drives.
But if it's a SAS backplane, you'll likely need to replace it. In this case, *just* get a SAS HBA and replace the backplane. Since the SAS2 backplane I mentioned (eg, the BPN-SAS2846EL1) includes a SAS Expander chipset, you can plug it directly into the HBA and hook up all 24 drives with a single cable.
2nd one seems cleaner with less cables, and the newer SAS HBA would have better support for things like SMART? e.g. I saw your server has a IBM M1015 which I assume works with no limitations and supports the 8/10TB drives too.
SMART is only for SATA drives.
Also, if it's passed on (and how) depends on the controller. And yes, my IBM ServeRAID card has absolutely no issue with 8TB drives or passing on SMART data
(Caveat, the specific firmware revision and driver version affect how the SMART data is passed on .... and may require the "Unsafe Direct IO" setting to be enabled).
But basically, the answer here is "Yes".