Adding external hard drive to system

Directv doesn't say anything about adding an esata 2TB external hard drive (only up to 1TB drives)......has anybody had luck adding a 2TB hard drive? Also, they "recommend" WD's and/or Seagates. What other brands have been successfully added? I'd like to add a 2TB, 7200 rpm unit with a 32 or 64mb cache? Any forseeable problems doing this?