I have my main PC and a mini htpc type thing and I am using them with one monitor and keyboard/mouse. I bought a cheap vga kvm switch off eBay and used 2 printer type USB leads to connect the machines to it, it works fine, press a button and I get the keyboard and mouse on each one. I am using DVI on main PC and VGA on mini PC on my monitor. I just use the buttons on monitor to switch. The thing is I wondered if I could share my speakers too? They only have one 3.5mm jack which goes to my main PC at the moment, could I just buy some Y adapter and plug both ends into the line out of the PC's? Or is it not possible? Closest I can find is this : http://www.ebay.co.uk/itm/231736379051
but its for microphone and headphone instead of headphone headphone.
I think you can get kvm switches with speakers/microphone inputs too which maybe the only solution, ideally I'd get a digital dvi/hdmi one but they are expensive