So lets stop for a second. Correct what I have wrong below:
Super Perfect Cell will be the baseline
SSJ2 Cell-saga Gohan: Stronger than SPC
SSJ1 Cell-saga Gohan: Weaker than SPC
Buu-saga pre-ultimate SSj2 Gohan: Weaker than SSJ2 Gohan
Dabura: Was it or wasn't it stated he was equivalent to Cell? From what I recall watching, he was matched up pretty evenly with Buu-saga pre-ultimate SSJ2 Gohan. Posters seem to have evidence showing that he was Cell-level in power
Broly: Way stronger than Buu-saga pre-ultimate SSJ2 Gohan, difference in power shows he'd beat Dabura easily.
So far we can assume a few things. SP Cell and Broly are definitely stronger than Buu-saga pre-ultimate SSJ2 Gohan. Broly being so much stronger means that he'd beat Dabura. If Dabura is Cell level in strength, then Broly could beat Cell.
Now-
Goku with the power given to him from Gohan, Trunks, Vegeta, Piccolo: Stronger than Broly.
That means in this form, Goku would beat Buu-saga pre-ultimate SSJ2 Gohan, and SP Cell.
It might even be debatable that Broly could stand toe-to-toe or even beat SSJ2 Cell-saga Gohan. That means Goku with their power absorbed could too.
So that leaves us with a tier like this right now:
Goku (Everyone's power absorbed, pre-SSJ2 Cell-saga Gohan)
-(Beats Broly)
Broly
-(If Dabura is Cell-level in power, and was about even with Buu-Gohan, Broly is much stronger than all of the below)
SSJ2 Cell-saga Gohan
-(Equal or stronger than SP Cell)
SP Cell
-(Equal to Dabura?)
Dabura
-(Stronger than the below Gohan, but equivalent supposedly to Cell)
Buu-saga pre-ultimate SSj2 Gohan