Your current Corsair 620w PSU is MUCH better than an Apevia 1100w POS.
Apevia PSUs are JUNK and can output no where near their rated power.
It would not surprise me one bit if your current 620w PSU can output more clean power than this supposed 1100w unit.
Stick with a quality Corsair, PCP&C, Seasonic or Antec Earthwatts PSU and do not worry about upgrading now.
Your current Corsair PSU has more than enough power to run your system.
On a side note, why are you adding a 4670 to a rig that already has a 4870?
Well said in my humble opinion.