Wozza365, not sure if we're talking about the same multitasking here; in my case I have a lot of apps running simultaneously on my Galaxy Note SGH-i717 (Android 4.1.2, 1GB Ram, Dualcore S3) such as Fongo, Juice Defender, EasyEyez, Onovo Extend and occasionally media player such as PVSTAR+ or Winamp in the background; usually with all those apps (not including the media players) I use a little over 600MB of available 743MB ram according to the task manager.
As soon as I load a media player or chrome, I notice my ram usage goes over 700MB and background apps start to close on their own; as far as I know that is because Android allocates more ram to the currently active app; as soon as I close the media player or chrome and ram frees up, I see my background apps start back up.
When using my friend's North American Galaxy S3 which has 2GB of ram, I noticed no such issues and I can run all my normal background apps, a media player and chrome with multiple tabs without having anything close on me.