Need advice purchasing a KVM device.

I'm looking to purchase 2 KVM devices. I have 2 workstations with each workstation having 3 PC's.
1. The first workstation has 3 PC's connected by a 32" samsung 720p HD TV as a monitor connected by 3 HDMI connections directly from the Video cards into the TV's 3 HDMI connections.
2. My second workstation has 3 PC's connected to 3 20" HP monitor's connected by VGA connectors.

My question is I would live to share a USB 2.0 keyboard, and Mouse at each workstation between all 3 PC'S. I want to leave my Video connections the way they are, and not use the KVM video connectors. Will most KVM devices function correctly if one chose not to use the KVM video connectors, and only used the KVM keyboard & mouse connectors? Will they function at all that way? I have never used one, but I really need one so I don't have keyboards, and mouse laying everywhere.

Also after reading many of the reviews at NewEgg it seems that most of them are not reliable so I don't know which one to choose. I want to keep it under $100 for each device, and I want it to have a push button switch. I was looking at Iogear. They had one I liked except it did not have a push button switch. Does anyone have any suggestions?