This may not be the answer you are looking for but I use RealVNC on my PCs. One PC is running with the monitor switched off to save power (unless I want to do a lot of work on it). I control both PCs from one PC, one mouse, one keyboard, one active monitor. The display from the second PC is sent over my LAN.
Yes you can actually. Get a KVM switch kit and don't connect the monitor off of the KVM connector cable. Use your monitors that you have connected to the towers. http://www.amazon.com/Switch-1-Keyboard-1-Mouse-1-Monitor-2-Computers/dp/B001UP2D2W