The 1TB is good in storage, but you need more that 4 partitions for a good administration of this, and for that you can make more that 4 partitions need convert the disk to dynamic. For a good performance of a dynamic disk, you need a RAID-5 o RAID-0.
You need the 32MB cache for the games, not for the OS. The 250GB is an IDE, isn't so fast how the SATA.
The 500GB you can partitioning on 60GB for OS and programs, and the unused space can be add to the 1TB.
Finally, you can use the 250GB for backup.