I'd use the Hitachi, if it was made to run under the SATA-2 spec.
Then -- IF I HAD SATA-3 ports on my motherboard with a recent Intel controller that allows for ISRT in BIOS RAID-mode and the software configuration, I'd buy something like a 60GB Mushkin Chronos or Patriot Blaze for $40 to $50.
If no SATA-3 on the motherboard, there's the option of picking up a $60 PCI-E SATA3 card controller; fit it to an x4 or x16(as x4) slot.
Install the OS on the HDD.
With ISRT and an Intel mobo controller, configure IRST for SSD-caching and acceleration of the HDD.
Without ISRT and Intel mobo controller, using the PCI-E controller, cable both the SSD and HDD to the controller. Some controllers have Marvel chip with Hyper-Duo, replacing ISRT.
If not, you have the option to buy $30-worth of rock solid software that would do it for any controller and a mix of AHCI and RAID-mode drives. But you would at least like to have SATA3/SATA-III capability in the system, so you still buy the PCI_E card.
Then calmly shop for an SSD of decent 512GB or 1TB capacity, and buy it next year after you save for a slowly declining price.
Or -- just buy a 512GB SSD and only consider the caching so you can add programs and datafiles alike on the HDD and get varying improvements ~= 80% of SATA3 SSD performance. In that case, you spend a lot up front, with only an option of spending the additional $100, or not spending it at all.