oooeeee yeah! glad you're on the eXtreme train, choo choooo
this is a great question, it's probably something i should include in the book, so thanks for that idea.
for recommendations, i'd say broadly anything by rob liefeld from that era (he's who i was channelling the most), but more specifically:
his run on new mutants. he starts on #86 and changes the paradigm of that book very quickly, and it's a pretty good indicator of how other people start making superhero comics in the years following.
x-force #1 follows on from the end of new mutants, and was the real game changer for sales. rob leaves around uhh issue 10 or so but is followed by greg capullo and it's still got the same vibes for quite a while.
youngblood is where rob moved to, having his own creator owned title. i'd say it's good reading for the vibes, but the writing is kind of all over the place, but it's fun to see just how wild and ludicrous it gets. just don't expect any great work of fiction and you'll be fine.
jim lee's run on x-men is more controlled and focussed, eventually he leaves to do wildC.A.T.S. at image. although not as solid a read as x-men, it's got the eXtreme vibes you want.
other eXtreme readings include: mcfarlane's run on spidey and then spawn, wetworks, death & return of superman, heroes reborn, spawn, savage dragon, shadowhawk, gen13, cyberforce, the MAXX, prophet
i could go on haha, i'll save it for when i add it to the book. most of these i've mentioned should be easy to find either in trades or online, hope it helps! i'd love to see what issues you come up with :)