Just don't rly know anything... if I was media watching I'd have as big a screen as possible, not a laptop.
Assuming you're travelling, there's a choice about whether you'd have 720p or 1080p media... then buy a laptop as cheap as possible that fits the bill.
Spose there's also the question of whether you'll always have it plugged in, or whether you need 3+ hours battery to make it through a movie... or 5+ hours to make it through an evening...