Ardour is professional hard-disc recording for MacOSX and Linux - meets all of you studio requirements.
Ardour packs features such as: multi-channel recording, non-linear and non-destructive editing, mixer functionality and uses time code to sync to other devices.
It also supports the LADSPA plug-ins for all kind of effects.
Ardour is a digital audio workstation. You can use it to record, edit and mix multi-track audio. You can produce your own CDs, mix video soundtracks, or just experiment with new ideas about music and sound.
Ardour capabilities include: multichannel recording, non-destructive editing with unlimited undo/redo, full automation support, a powerful mixer, unlimited tracks/busses/plugins, timecode synchronization, and hardware control from surfaces like the Mackie Control Universal. If you've been looking for a tool similar to ProTools, Nuendo, Pyramix, or Sequoia, you might have found it.