With so many typos, it’s a bit hard to take your post seriously. If you aren’t a spammer, you need to slow down and put a bit more thought and care into what you are doing.
- Do you have any estimate (GB) of the amount of data you are trying to back up/stream?
- Are you the only user, or are there more people in your household that will be streaming stuff at the same time?
- Do you have any experience choosing parts and building PCs?
The HL15 might be overkill for what you are trying to do and an HL8 or 4 might be a better choice. To run Plex, the typical recommendation is to use hardware transcoding which requires a GPU like an Intel A310.
- Do you have a higher end GPU currently for your gaming that you want to use in this system?
- I’m not a gamer, but I know a lot of games run mostly on Windows, and there is SteamOS for Linux. Are you just trying to run emulators for old game systems, or more modern games?
- Do you know anything about Linux or are you mainly a Windows user?
The connection speed to the internet and around your home can be different. Whether you can make use of the 5 gig from a single computer will depend on a number of factors. Without some planning, it would be more supporting, multiple concurrent users, eg 5 users each at 1 gig.