[TalynOne]

Running an official stock really isn't that important. As has been said you can run 6.5 on a Mogul / TP today if you wanted to. And Windows Mobile 6.1 can be loaded on a PPC-6700, even though there's no "official" release. Stock ROMs are usually so bloated and badly tweaked that it's almost a requirement to run a custom ROM to get acceptable performance.