I have a few on my desk.
Because of a fortunate job with porting our apps to Android I have the Nexus 7, Asus Transformer, Kindle Fire HD and a few others.
The Nexus 7 does not have HDMI of any kind so that knocked that one off your list. But it is a FINE tablet.
I have the Asus TF300T Transformer but it fails your micro usb requirement. It also has one speaker.
Where did you read the Nexus 7 had HDMI?
And about gaming. It's tablet gaming, nothing like a PC so be sure you are into that.