5-6 rows of Pawns??
Such a variant is known under the name Lord Dunsany's Game ( http://www.chessvariants.org/unequal.dir/dunsany.html ) with only 4 ranks of Pawns, and I always thought it was already won there for the Pawn horde, if they played carefully.
If you like this sort of asymmetric game: Charge of the Light Brigade ( http://www.chessvariants.org/index/msdisplay.php?itemid=MSchargeofthelig ) is another one, which plays (next to the usual King and Pawns) 7 Knights versus 3 Queens.
I love 960, but Horde is maybe the most fun I've had with a variant in years, because it uses the rules of real chess from a very different set-up. Basically, White plays 5-6 rows of pawns, and black gets all of their pieces and pawns. Black tries to eliminate all of white's pawns, while white tries to checkmate the black king. They started it out with colors reversed (i.e. Black playing the Horde), but that favored White to almost a 75% win rate. So with the color flip, its probably preferable to play Black, but with an opening advantage closer to traditional chess.