How large do you feel comfortable printing with the 5d?
With interpolation and other image sizing software, you can print quite large (Define large?) when factoring in appropriate viewing distances. I've done native resolution prints at 130-135 and they come out pretty nice on the Cymbolic Sciences Lightjet, Durst and currently Chromira printers. Nice to have more for a given print size but that has been my experience without interpolation, my usual print sizes were 20x30" and 30x40".
At home on the Epson R3000, 13x19" is fine and at arms length it is a bit soft. When viewed on the wall, it is fine.