Save yoursdelf about half...
The bottleneck isn't going to be the processor for streaming, it will be the Hard Drive and Front Side Bus.
A 10,000 RPM Western Digital 74GB Raptor would be better than a 160 Gig 7200 rpm drive. ($178.00 NewEgg)
The 800 MB Front side bus is definitely a plus and the 512M RAM is OK too but not that important.
Processor speed isn't as important for a streaming server because you could stream with a 2.0 ghz or even slower.
You are ideally going to be limited to 100MB per sec by your NIC card then even slower by internet connection if you are going to run it at your house/business unless you have a T1 or T3 connection. Most DSL connections are 384kb per second upstream or less.
If you decide to go to the computer show, look for something with an 800 FSB and SATA drive interface.
See if you can find a Raptor drive or another 10,000 RPM drive for about the price above.
You should be able to put together a screamin streamin server for $600-700.00 on the top end.
Try starting here to get an idea on prices before you go:
http://www.pricewatch.com and search for a system there.
or to give you an idea:
http://www.portatech.com/catalog/products.asp?ID=222
I've not dealt with them directly but Pricewatch.com listed 148 satisfied buyers.
Your only other option would be to house it on the satelliteguys server because your provider has multiple redundant connections to the internet backbone.