Sony Vaio or a Toshiba Qosimo.
Are you dead-set on a laptop? They really aren't as good as you might think, despite their portability.
Have you considered an HTPC?
I dont think you would need MCE for a USB tuner and you will NOT need a special card for it. try pricewatch.com or newegg.com. :D if you use pricewatch.com check the stores rating with resellerratings.com i suggest newegg.com they are good
As someone said, a Vaio would probabley be best. I seem to remembe most at around 1200 dollars having t.v. tuners. You should try to get 80GB of hard drive and at least 512 MB of RAM, and whatever you do, don't get a Celleron processor.
They've been around in USB for many years.
I bought one for my wife's XP laptop, but with all the other things she runs on it I've never had occasion to actually install and use it.
I'd suggest you try Ebay. The one I bought was under $100 new, and operation sounded simple. No extra cards were required.
Scroll down, it's on the left side under the section "New at Dell" talking about Media Center 2005. They've had this for one or two years I believe, since Media Edition came out.
I think you've hit on the solution, if you're set on a laptop. You don't need MCE for a USB tuner, and unless you're planning on the laptop doubling as a home theater, just about any laptop screen will comfortably handle non-HD TV resolution - DVDs top out at 720x480, and laptops pretty much have a bare minimum resolution of 1024x768 these days