I would go with a SATA interface optical drive instead.
Raid 1 is not really worth the cost in general computer use. And Raid 0 is not worth the risk.
You should purchase an OEM version of Windows XP. See if you can find one with a coupon to upgrade to Vista. I would wait for until the first service pack is released before upgrading to Vista.
As for a TV tuner... I love the Hauppauge lineup of tuners. You may want to consider getting Windows XP MCE if this build is going to serve as an HTPC also.