Monitor sharing

[BritSwedeGuy]

I have two PCs and two monitors (15 pin connection) but this seems a bit redundant and I would like to switch to just one monitor. The towers will be near to each other.
Recommendations?

 

[BritSwedeGuy]

I'll be keeping one of my two existing monitors, I just want a switch box to be able to change between them. One is an always on server, the other my 'power machine', so I don't need to see both monitors at the same time.
I've seen a box but it did mention loss of signal quality, which isn't something I want.