As I am limited for space I would like to get a vesa mount when I get a 24" iMac. Are there any wall mounts that as well as going in and out, also go up and down. I want this because of the way that my room is set up, I have speakers in each corner of my room at one end connected to an amp and so when watching movies on the imac it would be ideal to be central to these, also as all my cables are under the floorboards its a little hard to change. So when using the imac for watching movies etc it would be nice if it can go a little lower. Are these mounts ok on hollow (plaserboard) walls or is this a definate no go?