I'd install 7.6.1 just to get a running system and then get a memory upgrade and boost it up to 8.1. The difference in overhead between 7.6.1 and 8.1 is not huge and the 4400 is fast enough that 8.1 won't make it snail slow. It's not until you start getting into 8.5 or higher that overhead starts to become a problem on older machines with limited resources.