I had read that story, it was on a webring, i started from the part / book where they got the job training new heros because they used to be in a team that died & the reason they can change gender is because of that event that killed them, they mergedor somethingand got all the powers? they were...are still a speedster originally, so thats why they were hired to teach new heros at what turned out to be a super villains base.
i actually went out to try and find it again, found the very book you linked but the first book is so different...and bad, that i thought that i got it wrong.
Now im going to try power through!