I would go with Gjoerulv's hardcore mod for exact story + much harder bosses. If you try that one, then I recommend spending a bit of time in Reactor 1 scouting around and gathering up stuff as the mod has a lot of new items available on enemies that can be very useful (that and you'll want some healing stuff to deal with the boss as I tend to find the potions given at the start don't quite last the battle).