You AMD based Asus Crosshair 1 motherboard with a Nvidia chipset was introduced in 2006. The motherboard was manufactured several years before consumer ssd's became popular. The motherboard and chipset do not support AHCI mode or modern 3rd generation solid state drives. The motherboard is no longer in production. There are are no system BIOS or chipset updates.
Well I updated the firmware by putting the drive in my laptop. the benchmark magician software gives me 279 mb/sec sequential read and 137 write.
Random read was 21814, Random write 20277. These are lower but expected due to sata 2 and no AHCI support.
So I am possibly set up as best I can till this upgrade you suggest.
You do have the option of an add in controller card if you have pci3 v2 slots available. Something like the $30 syba probably wouldn't show an increase but the $70 highpoit Rocket 640l should give you full speed.