Convert PowerMac to server or external hard drive?

I need a way to store large files off of my MacBook Pro, but still be able to access some of them readily. Here's my situation: I edit video, and I've recently gotten involved in my school's video club. I'll probably be the primary editor for them, so I need somewhere to store all of the video. Back before I switched, I worked on my sorry PC that I put a 160 GB drive in. I need a storage solution that will be able to transmit and recieve the video quickly while I'm working on it. I've considered several options, but I don't know if there will be severe bottlenecks in them. I'll explain them, and I'd appreciate your feedback.

I've recently gotten the notion that I can use an old Power Mac as a server to host some of my larger files. First of all, I'd like to know if my expectations are reasonable. Here they are:

Store vast amounts of data, likely over 300 GB
Be accessible wirelessly, whether by AirPort or a wired connection to a router
Be accessible wired, for large file transfers

This option seems to be a bit more cost effective and scalable as opposed to the other option I've thought of, an external hard drive. However, I'm not sure if even a wired ethernet connection could handle video editing. If this would work, what kind of Power Mac would be required? G3? G4? Dual G4?

The other option would be an external hard drive, I suppose connected either by FireWire or USB2.0.

Thanks!