ExtraCells is a mod by M3gaFr3ak that is an addon for Applied Energistics. It adds bigger storage drives all the way up to 16M (250 times larger than the current 64k), fluid storage on seperate drives made for just this going up to 64k, other type of storage drives, and a few utility blocks such as the ME item dropper or the ME blast resistant drive. http://www.minecraftforum.net/topic/1801643-ae-add-onm3gas-extracells-169d2020/ It's currently out as beta for 1.7.2 , and full release on 1.6.x. This would be a nice addon to have, imo, for those who enjoy AE alot and want to have something a little more end-game by getting those 16M drives who are hard to craft and needs tons and tons of reasources. I am not sure how well this mod will run so tests will be needed to see if it reduces perfomance alot, though I think an addon like this won't have that much of an impact.
We had this on 1.5, but it became buggy on 1.6 for some reason. (or something... there was a particular removal reason)
I know for a fact that the spatial storage (which can remove areas out of the worlds, save them, and replace them) is buggy. However, this can easily be disabled by disabling the items needed for it, maybe even through an option. So it cannot be the only reason. I've often used it for larger cells and fluid storage and I never noticed performance issues or crashiness.
