Pretty good, no reason to change any parts that I can see (except maybe low profile RAM so you can add as large a heatsink as you want, G.Skill Ares and Corsair Low Profile are good kits to get).
I recommend the OCZ Vertex 4, its a great SSD that fights for fastest in most benchmarks.
Considering you have an SSD, HDD performance doesn't matter that much. Only reason to get another/upgrade would be more capacity. Maybe if you install your games to there it might help getting a new one, but the benefit will be small.