if your g620 does not support vt-x then it is disabled in the bios. see
compared to i3 you dont have got ht and no quick sync (hardware h264 encoder). i3 vs. i5 means no aes commands thats similar to standard phenom vs. fx cpus, those fx cpus have got aes instructions. i5/i7 feature also a turbo mode which simpler cpus lack. usually i5 is not only dual (but there are some dual) but quad. i7 is usually quad + ht. the mobile variants are however dual without a Q in the name. somehow a bit confusing if you never looked at intel specs. for amd you just need to choose fx series when you want aes.