I have four servers, each has the following specs:

Xeon Quad Core 2.13GHz
4GB RAM
500GB HD

And they all push 800mbps in bandwidth. My I/O Wait for the discs are very high, like at 80-90%. I was wondering if putting them in RAID 0 would help me cut that load in half and if adding more memory would also help.

Also, please note that the files I serve are 200mb in size, average.

1. Sure, a RAID 0 will improve performance, but it will only be helpful if there aren't too many writes. It's better to go for better hard drives in RAID 0 though. For example, if you currently have are using PATA IDE, move to a better server with SATA. If you currently have SATA-I with 2-8mb cache, try SATA-II with 8-16mb cache and so on.

2. If you want to add more memory instead, then look into apache's module mod_file_cache to map the most accessed files into the memory.

3. Disable access logs completely or for certain type of files. This is useful if you have a server with unmetered data transfer.