What kind of computer shall I Get?

I have an idea hocking up my TV to the computer which I'm doing so now. Do you recommend to get a laptop or just desktop. My use is mainly Downloads heavily like movies surfing the internet for long hours.

I'm using a Lenovo G500 that I bought last year. But I want to upgrade. IF you give me a link or what to get please help

First of all, I need to know if you have any kind of budget because there are so many options out there, but a lot of them are quite expensive. Or, tell me if you maybe would want to build a custom one because that's sometimes way cheaper. Also, if you are hooking it up to a TV then there's no point in getting a laptop with a screen that costs extra money. So desktop would be the best choice.

Acer