Thanks for your response.
I bought a monitor for my son, a Phillips 22", online, and when I looked at it I thought it would be compatible with the MaC Mini (the blurb said it is an HD monitor and I suppose it is) and with the PS3, but, but it clearly isn't, so today I went and bought a VGA to thunderbolt cable to make the Mac Mini work with the monitor, and it does, but I think I now need a VGA to HDMI cable to make the PS3 work.
My son is currently playing his PS 3 and looking at a 32" Sony Bravia HD monitor from about 3 feet away, and it is really hard on the eyes, (in the long run I'm trying to save on optician bills, as one does).
What to do?