I apologize for going a bit sideways here, but I still find that you will get the best use out of "purpose built" products. Buy a TV to use as a TV. Buy a computer to use as a computer. Putting a small replacement digital TV in the space of your current TV will give you the best picture and service and you will be able to use your computer at the same time you are watching TV. This also gives you some added freedom in your choice of computers especially when it comes to size. A 17"+ laptop is a big piece of hardware and should you want to take it along on a trip you may rethink that while if you had a more reasonably sized laptop it would not be such a big deal.
Anyway, just thinking out loud. Compare the cost of a TV tuner to the cost of a replacement TV and the cost of the laptops at various sizes to make sure you end up with something you won't regret.
