If I watercool, then I need the depth for manifolds, hose, and other apparatus, so the PSUs would still have to stack, but all of it could probably be crammed into 6 or 7 total U. As much as I would love to have a package system, I doubt I could fit an appropriate radiator and pump into that space, so it would probably have to be external like DeathAndTaxes' setup. BTW, has anyone actually done any long term tests with more than 2 watercooled cards directly adjacent to each other without a second slot in between? The more I consider it, the more I am sure it would be prone to failure, unless they weren't linked directly to each other. If that were the case, I would have to use right angle connectors on each and every card, and that would get tedious, real fast.