as for distribution? just about ANY distribution should work, if you are familiar with ubuntu then I see no reason why you shoudn't stick with ubuntu.
as for hardware? you could start [ur='http://www.linuxquestions.org/hcl/']here[/url]
there are several ways you could set-up a pvr, but the most bare-bones is a video card that outputs as an MPEG stream, ffmpeg and cron
or there's [url='http://www.mythbuntu.org/']mythubuntu[/code] an ubuntu based distribution based around MythTV
either way, good luck