Advice for MBP configuration for photo/video prosumer

Looking for some help for a setup using a MacBook Pro with a fair amount of photo/video work, and the current machine isn't moving as quickly as it seemingly once did (I can never figure out when the drives need to spin up (all 4 of them, and why), and also why it sounds like the machine is accessing the drives when I seemingly am doing nothing).

Current setup is :

Mac Pro

4 x 1TB (Hitachi 7200) drives. One drive is boot + more, and a second drive is for video. The other 2 drives are clones. Ddrives are 700-800GB full.

2 x 2.8 Quad-Core Intel Xeon

4 GB 800 MHz DDR2

NVIDIA GeForce 8800GT

I don't know the most "efficient" setup is to get to a faster and better solution. I'm looking at MBPs since I will also need to be able to take the machine with me, though I don't mind being tied to editing the files at home where I have a much larger screen.

My best guess is a MBP 15" Retina with

512GB flash (not sure 768GB is needed)

2.7GHz? (not sure of the benefit of the 2.8GHz)

I'm guessing the 512GB flash is acceptable, since I'm thinking I should be storing all photo and video files on external drives. I don't know if by having all files on external drives however will slow thigns down, or if Thunderbolt and external drives (I am assuing 7200, maybe even keeping my current drives?) will be even faster than my current setup. I really want to keep the workflow as super-basic as possible, without transferring files manually back and forth. I haven't bought a machine in ages, so not sure even where to begin.

I'm guessing some type of RAID system (while I am closing in on 2TB of files, I would think I should be thinking about having ~3TB of photo and video files). However, I know not a thing about RAID systems, and want to be sensible about having everything backed up (I would prefer to have local backups, and then consider cloud separately as well).

Thanks in advance for any advice. Much much appreciated-