CPU 2.80GHz & Ram 1.0GB seems ok...see below photo. My suggestion is add 1GB more if you buy TV Card (now is below HK$200/1GB)
My spec is Inter(R)Core(TM)2 CPU 6300 @ 1.86GHz, 2.98GB RAM, 250GB HARDDISK
Yes. my suggestion is add 1GB RAM. And also make sure your motherboard is use PCI2.2 插槽 if you buy this card. If not, there are many choices, go to have a look.
ps. 你唔係買左高清盒咩, why need to buy高清卡?