, is not it an "overkill" for a 7 year old cpu/ram ? (which are ddr 1-pc3200 ddr 400 mhz rams)
Depends on the game. Some games use virtually no CPU power whatsoever, some like loads. At least it's a dual core processor, and most games will at least be playable with a dual core. My other PC has an old Core 2 Duo @ 2.5Ghz (E5300). It won't play Crysis 3 or Planetside 2, but most other games run just fine.
Have you tried Steam Homestream? I'm in the beta test and works great streaming games to my 7 year old laptop. This would make a great box to stream games to. https://steamcommunity.com/groups/homestream