Help with upgrading office network.

[katharsis]

Been having some trouble at my office for some time now, mostly with our ISP, Oceanic Cable that belongs to Time Warner.
We got a 5/5 MB (with 3/3 MB guaranteed) dedicated line but our speeds shared on 8-10 workstations just sucks.

Mainly the up and download to our main servers in Europe. I do understand that it is a long way from the US and its being capped at some point. But I am getting the same rates with my home cable internet that I do with a dedicated business line at a tiny portion of its cost.

So we recently found a new provider who gives us 10/10 MB at any given time with 99.99% uptime. So far so good, the overall experience has definitely increased, however the upload to our servers is just all messed up.

On most PCs (all are running XP Pro) I only get 70 KB/s ... on 2 of them I get up to 140 KB/s and on our Mac Pro I get 280 KB/s !!

Here is the basic setup:

modem - 4-port switch - 3 individual routers - workstations

This is the same setup as it has been before and all computers had an upload rate of about 100 KB/s

So I tried switching the routers and cabling. Nothing!
Been using CAT 5e and CAT 6 cables (which the CAT 6 seem to be bring a bit higher speeds than the 5e)

Could this have something to do with the computers network cards ???

It's pretty frustrating at the moment and the new ISP will run some tests as they are not sure what might be causing this.

Any input is much appreciated.