G-RAID Mini 1TB 0G01652 - upgrade drives?

I have an old G-Raid Mini 1 TB (dual 500g 7200 RPM HDs) model 0G01652. It works great but is a bit on the small side for what I need lately.

Is it possible to replace the internal drives with larger drives? If so, what kind of drives will work (size, brand, model) or will any 2.5" drive work with the appropriate interface (SATA, i assume)? Also, Can I put in dual SSD drives to improve the disk speeds, or would that not matter because of speed limitations on the I/O interface(s)?

I am using it on USB 2.0 with Windows in a dual 500GB RAID 1 config.