2x Athlon 2600+
2x Xeon 2.4
both with 1 gig of ram would be a nice server.
But I'm sure if you wanted to spend some money, you could go wiuth the quad servers out there
I did a quick search on google for sites that provide them as basic packages here are a few:
http://servers.aplus.net
http://www.2clones.com/dedicated_unix.html
http://www.xgforce.com/eService.html
but keep in mind like we do, most companies will do custom servers not on there packages. We require contracts though if we have to build a custom server. I'm aware of 5 other providers that will also do this with contracts.
as you see thugh quad servers will set you back alot. Unless you decide to colo. I'd stick to dual dedicated servers. Unless there is a need for quad.
Though as a businessman, I'd like to offer you a quad server :-p