I have a site that runs with xfilesharingpro. I already have several severs implemented however downloads are slow on some averaging around 80kbs.

I'm still wondering while buying a server what are the specs that are most important in a file download site?

For example, CPU, RAM, Port speed

I have around 6 servers and they currently have a Quad core, 4GB RAM, 1Gbps Port

Is there something else i need?

Note: My site averages around 150k visitors and 80k downloads p/day