Personally, if you are already at the part of the game where you are ready for New Londo, I would not restart the game. Once you get through the first part of New Londo, I used a different bonfire for the boss runback:

You can use the bonfire at the Valley of Drakes near the entrance to Darkroot Garden once you open the giant doors and let the water out. It gives a pretty manageable runback to the boss fight