If you are looking to spend more than $500 on a high end computer, you should look to build your own desktop tower. It gives freedom to build to your liking. You do not have to deal with software that comes on most computers factory built that you do not need and slows your computer down. You know that quality parts are used which insures its up most reliability.

where would I buy computer parts online?
Newegg.com
Where would I buy computer parts locally?
Intrex computers or Compusa

Tablets are on the rise, and there is much talk. There is not much to say here outside of preferences. With that said, my preference is a android tablet. You really do get what you pay for. I don't think you can do better than $250 for a 7" tablet and $400 for a 10" tablet. Which one should you get? Almost weekly this changes. Feel free to email me if you want to know my current thoughts. I tend to stay up on what is out and coming up.

Unless you are required to use a laptop most of the time given your specific situation, I would not advise buying a large or high end laptop. stick with cheap and mobile, like a netbook or even better an android tablet. But, if you must have windows, I would personally go with a Lenovo netbook and reformat the hard drive to get ride of all the blot software.

I would not buy any laptops local. I would buy direct or from sites like buy.com.
as a side note, any time you are able to distance yourself from windows, it is a very good idea to do so. go with something like a android tablet as a alternative. 

Android all the way. If you buy it get it at best buy. They have the best service and the best insurance.