I'm not sure on the cable but I think it's cat 5.
The test I'm doing is copying an ISO file from a server downstairs with an SATA hard drive running Gentoo Linux to a computer in the normal middle floor with an SATA hard drive running Windows Vista/Gentoo Linux (Vista has a speed of about 2MB/s - 12MB/s and Gentoo about 12MB/s - 24MB/s).
Edit: I just looked at the cable and it says "Enhanced Cat 5 UDP 350Mhz CM 75C UDP 4PR 24AWP".
Edit 2: My server has two Xean 2.4Ghz processors and my main computer has a Quad Core 2.4Ghz processor.
My router is a D-Link DIR-655.
Edit 3: I suppose I could test the transfer between the server and the media center which are closer together. I'll just have to find a speed report tool for Linux.
I'll see about this tomorrow though as I'm going to bed now (A bit earlier then I've been getting to bed).