For this specification I suggest for you Avira or NOD32 because it is system friendly scanning option.
I think you should go for the Avira. It is very low in the memory and quite faster yet effective than others.
Kaspersky antivirus i am using before last 3 years its better for my computer system and have secure that to unwanted things and threads which are downloading from internet..
Kaspersky is good, but with the given resources, i think you should look for a lighter one MSE is the best for your computer, but you can give another thought to Avast as well
you can choose the AVG free version. it only contain the basic functions but they are enough for a regular pc