No matter what kind of CAT5E or CAT6 cable you use, you're not going to get 1000mbps since the port of the cable modem is only 100mpbs and the actually speed of your connection is probably less than 10mbps.
Even 10Mbps is optimistic. Most of the time you can pay for 10, but they really only offer "up to 10Mbps". You'll probably get somewhere in the neighborhood of 3-5Mbps down and probably less than 1Mbps up.
A lot of folks get confused about transfer rates through a network. There are intranet and internet. The Intranet is the network inside your home. If you have more than one PC connected to the router you can transfer data at a higher rate than the speed you get through the internet. The internet is governed by your ISP. Those rates that are given are maximums and are seldom what the user experiences in real life.
When transferring files from one PC to another (Intranet) you will be limited by the speed of your NIC cards, cable type (Cat5, Cat5e, Cat6), Hard drive access/throughput, etc. So even if you have Cat6 cable and 1 Gig NIC cards, Gig router/switches you will not get 1 GB throughput if your Hard Drives rate is 100 meg.
Timby, your final statement is misleading. A 1000Gb connection is 125MB, so if you have a raid array, ignoring overhead, you could saturate this. Realistically only about 800Mb of the 1000 is available, so you could get by with a raid array capable of 100MB. Gotta keep the Mb, MB and Gb, GB straight, use the rule of 8! BTW, gigabyte does NOT need anything over cat5e, I've run lines around 700ft that transfer near 700Mb over cat5e. The "limit" for ethernet is 100m or around 300 feet. Just make sure it's not cheap dollar store cable.
I was referring to in general (not that an optimized system with high end hardware). In general (meaning most folks) will not be able to get 1 Giga-bit throughput on their LAN as they will be limited to their SATA drives (not high end Rapter HD's running in RAID configs), older Cat5 cables and having other PCs connected that are running 10/100 MB. Also, just because there are instances of folks being able to run Giga-bit across CAT5 and CAT5e doesn't mean that it will work in all instances. If that were so the cable mfgs folks would tell you to use CAT5 for Giga-bit.
What is misleading is the fact that the folks selling the hardware do not explain to folks the 1 Gig-bit transfer rate is maximum and not typical.
if anyone is still responding to this, i'm looking for a little clarification. i want to buy a buddy a new switch for his lan party. is there any reason to get a switch that is 10/100/100 vs one that is just 10/100 then?