What is this computer gonna be doing? You didn't mention.
If you're just gonna be internet surfing & what not, the G550 is more than ample for several years, I don't know about 8, but I'd say 3-4.
If you're gonna be gaming, G2120 man.
You probably also are gonna want a GPU so that it'll be solid for years, a 7750 will be ample for a low price.