This will be my first custom build and I'm pretty set on most parts. Just after any further recommendations to make sure it should all run nice and smoothly. Main usage will be for gaming. Top budget is around 1.2k.
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.