format means prepare a HDD to be written and read to. partition is divide a HDD into different sections, usually labeled c, e, f, g, etc. When you say "old drive" do you mean stock hdd? If that is the case, and you've already installed xbmc and have that working, you are all good to go.
Unfortunately, no one listed the partition sizes on a stock drive, so we can't compare. I'm not even sure if partition size matters, though someone has said it did, but i read that it didn't matter. I think the most important thing is that you have unaltered stock files, such as unaltered MS dash, or MS update.
oh and those programs do formating and partitioning which also can be done by the x3 i guess. I guess the x3 prolly partitions the drive to stock settings, but with an f or g drive. It sounds to me like you should ok.