I've a bit of experience with this stuff. My job includes (among many other things) video editing using a NLE. RAID is definately the way to go.
First, off, at home for my media center storage system, I use a Promise RAID 5 card in a (Linux) PC that's connected to my network via Gigabit ethernet and have had no real issues. Sometimes with large video files there is a bit of a delay before playback begins or ends, but it isn't long and doesn't apply to audio. I did make very sure to use reliable network components (as opposed to the Marvell onboard Gigabit ports on my motherboards which I had lots of problems with). I love the system, but I don't know that I'd recommend it to someone who doesn't have a lot of networking and hardware-building experience... Plus, if you want to edit video, keep reading.
The stuff I'm using:
Intel Pro/1000 MT (Server) Gigabit Ethernet PCI Card (in the Linux server machine)
Intel Pro/1000 GT (Desktop) Gigabit Ethernet PCI Card (in other "client" machines)
Promise FastTrak S150 SX4 (non-M) with 128MB RAM installed (Kingston RAM)
4x Western Digital Caviar RE (Raid Edition) SATA 250GB Hard Drives (WD2500SD)
ASUS A7N8X-E Deluxe Motherboard, AMD Athlon XP-M 2500+ CPU, and OCZ DDR400 Memory, Antec Case and TruePower 450 Watt Power Supply
It works PERFECTLY. But....
However, I'd really recommend that you take a look at this instead. The
WiebeTech RT5. I have one of these at work that I use for all my video editing on my G5 with Final Cut Pro. It was simple as hell to set up, includes 2x Firewire 800, 1xUSB2, and 1xSATA150 ports. It's OS independant (just shows up as a FireWire drive or whatever) has space for 5 PATA drives (I'm using 5xWD2500SB with one in Hot Spare mode). You can even connect it to more than one computer at a time, if you've got the right interfaces on your PC (you can use FireWire or USB on one machine and SATA on the other). If you buy a bare system (with no drives) you can configure it however you want, and it's not too expensive (compared to building and maintaining a whole separate PC). AND, it's got a handle! It's quite heavy with 5 drives installed, but it is somewhat mobile (and you mentioned you use a laptop so I imagine this could come in handy).
Best of all, it's FAST. If you plan to use it to encode video, or live-edit video using anything approaching a Pro solution, Gigabit ethernet won't be fast enough. It'll drop frames when you're encoding, and slow down render and compression times. It seems like it should be, but once you add in the network overhead, it really isn't the same as having a local drive. In raw speed it's comparable, but Network latency (the time between when you request a file and when you start to receive a data stream) is HUGE compared to a local drive.
EDIT: I forgot to mention, I have a Hawking Technology 8-port Gigabit Ethernet switch. It's a great little switch with a nice backplane that supports full speed on each port.