ok ang ITX TS. I would go for that kay nice to have a Small Form Factor (SFF) build unya minimalist ang approach while not sacrificing on performance.
If kaya sa budget, I would go with the 256 GB ssd for system drive and the hdd can be secondary storage.
Dako gyud na'g impact sa responsiveness as well as boot and load times.
An alternative setup would be to buy a 64GB ssd then enable ssd caching with your 1tb 7200 seagate para your system will see them as a single drive.
With the money saved, you can opt for faster videocard or spend for peripherals.