it would depend on your hardware. if you have an old IDE drive, then you are going to have an issue no matter what. to improve performance, i would imagine you'd need multiple IDE drives to increase the number of readers.

if you have a SATA drive (newer ones are 3Gbps)... it's going to be tough for wow to fill that pipe, even with 5 wows. this would be like having 600Mbps per wow... which is comparable to the IDE speeds of around 133MBps or about 1Gbps due to additional caching effects. so, if your wow runs fine solo on an IDE, then it should be about the same for 5 on a SATA drive

another factor is using junction points. i have not used them, but i have spoken with people that have. my guess would be the improved performance may be coming from a cache within each junction point... but that's just a guess

just my 2cp worth....