internal raid set up for red editing

hello every one
i have a 2 x 3 GHz Quad Core Intel Xeon Mac Pro
with 4 GB 800 MHZ Ram
internal apple raid card
4 X 1TB Hitachi Sata Drives and one external 1TB Graid2

I am trying to figure out what would be the best way to handle Red footage with Final Cut Studio2
and my Mac Pro. I read many of the posts that recommend kona 3 and various external raid boxes.
I will be getting red footage and i want to know that i my set up can handle this footage

My question is:

1) What would be the best way to utilize my existing Mac pro in terms of speed and backup? Should i build a raid-5 with 3 1TB internal drives and keep the 4th drive for OSX and applications while backing up the original footage to external hard drives?

2) Can i start off editing RED footage with my current set up and what would be the best path to grow my setup? External raid box? Do i need much more RAM?

2) From reading some of the posts i understood that importing the red footage is not the problem but rendering and monitoring while editing is where the raid and kona card is needed, is that true?

3) I know that if i have a raid-5 on 3 1TB i will have 2TB available capacity.
assuming i will be editing with pro res will this set up be enough for a few 1hr documentaries and a few music videos or more
how do i make this calculations, i want to be able to have a workflow and set up where i can expand as my requirements grow.

4) I know there is not one magic formula. I read about 200mg/s-300mg/sec throughput and one or two layers of uncompressed or 2k realtime editng and i got a bit confused. Can someone explain
I will be finishing in HD or 2k

5) kona 3 or deckline HD extreme? for monitoring

Thank you and i want to thank all you pro's that are continuously helping and giving your time on these forrums, it really helps us

Danny

mac pro