I only have Goku 1.3x stronger than Vegeta or so and don't think Cell raised his power when he raised his speed, going by him not damaging Gohan at all with that kiai.
The advantage SSJ2 Gohan had over Cell was bigger than the one SSJ Gohan had over Vegeta and Trunks, IMO (though they're both huge). Either one is enough to beat his full power.