Man those remind me of my buddy and I who put a modified TT Jet AthlonXP heatsink on a 5200 for the hell of it. In his case, it had no purpose other than it was funny as hell and no one wanted to mess with their worthwhile cards so we had to use the 5200. We stuck on an old 90mm fan from a PSU on it; was almost wider than the card...=)
Either way, that's cool, but since the x850XTPE and x800XTPE are the same thing with some mhz differences, it makes perfect sense that some crazy ass aftermarket cooling does in fact make them overclockable to the same level. But as for usefulness, I'd much rather stick a waterblock on a card than use 4 fans. Those kind of mods are, like I said above, only really fun for use with old hardware that you have sitting around that'll give a good laugh.