As long as you have IOS58 and cios249, you should be able to use a 1TB external.
A few things Ive found regarding my old 1TB Seagate and homebrew:
Sone seagates go into hybernate mode, which can cause issues with usb support. You could try downloading Seagate's tool to disable this but it didnt work for me.
Ntfs support is very bad right now, with only a handful of apps that can read data. I'd reccomend formatting it as FAT32 if you haven't already.