Antec is a good brand, its just 650W doesn't leave any headroom left if you're considering an 560Ti/570 SLI setup imo. I'd rather recommend a 750/850W just to have the headroom so you're not making your psu work @ 100% load all the time.
As for the parts you've put together, all will run just great, including the Corsair ram

For the HDD, the size depends on how much storage you want personally and only get the 7200rpm hard drives for performance.
I would go for the G510 keyboard myself, the included screen for showing cpu temps volts clock rates etc plus game stats and vent/teamspeak info is a huge benefit imo over the G110.
For a mouse, I often find the M500/G500 or G9x being recommended for good gaming mice, besides the Razer DeathAdder or Naga, and the Microsoft Sidewinder X5. Those would be my choices to start looking at 1st and then going from there if they aren't to your liking.
Honestly I can't see the point in putting in a small ssd (say around 20/40GB) just for the OS as you're not putting any programs or games on there since you have to leave some space free, just like you would for a hard drive. You could get a 60GB and set it up for caching instead, using Intel's SRT, or get a 120GB and be happy to be able to put the OS, some programs and some games onto it before allocating the rest to the hard drive/s.
Good luck with your choices & enjoy the upgrades