You can mirror your upstairs desktop screen to your TV. Your desktop needs to have a wireless card of some sort. You're pretty much plugging in Chromecast to your TV as a wireless receiver.
It's about a 1400-1800NT investment. If you have friends overseas (in the states), you can probably get it for around 30USD when it's on sale.
I can't guarantee this will give you a super clear screen on your TV because it depends on how well the two units' WIFI connection is, but it's a much much cheaper solution than a new PC.