Your CPU is 4 cores, the other 4 are virtual and don't actually count since games don't really use them.
Either way your CPU and RAM is set for new releases, the graphics setup is excellent, but it really depends on your resolution and types of games. At 1080P I'd say you would have most games maxed out pretty easily.
If you have a good case it shouldn't. Make sure you have appropriate exhaust and intake and you will be fine. If heat is still an issue, buy a PCI slot based fan or separate the cards through a slot. I cannot imagine 550's having a heat issue though.