THIS IS NOT A BAD CHOICE ON THE CHEAP CP1-AM2-6400A MADE BY amd.Though depending on what the server is being used for.If you are working for or own the company.Depending on how much growth your company might predict in the future <a href="http://www.intel.com/products/processor/xeon7000/index.htm?iid=technology_quadcore_index+body_xeon7000">dual/quad xeon</a> (http://www.intel.com/products/processor/xeon7000/index.htm?iid=technology_quadcore_index+body_xeon7000)might be the best way to go.Dont let possible enviroment of the server room get hot think green.When its time to upgrade your possibilities your boss will apreciate you for his roi.As far as clock speed this can be a touchy situation under most circumstances while in full operation(under full workload) of all employees logged in moniter task manager and watch the cpu usage monitoring is key here. if it is under 15% leave alone no reason to cause more work on the cpu.If the percentage is hire think about more ram so insructions and algorythems have more space to go to.This should bring down the bottle neck on cpu in theory you should be lower than 15% you can increase speeds in increments.Good luck!!
With SQL Server more RAM is always better. Buy what you can afford. 4 Gigs is usually the minimum. How much data will be changing within your database? The more RAM that you have the more data SQL Server will cache into RAM.
As for CPU speed, any of the CPUs which are available will be fine. You'll want to get as many cores as you can. A couple of AMD 64bit quad core CPUs will be just fine, if not overkill for the workload you are talking about. As long as your databases are properly indexed and optimized a single dual core CPU will probably be just fine. That said, be sure to plan for the future. It's easier to buy a bigger box now, than to explain why the 1 year old server needs to be replaced. What do you think the work load will be like in 12-36 months?
Page file should be set for a couple of Gigs. You don't want SQL Server to be able to page to much data as it's easier for SQL to load the data from disk than from the page file.
Some articles which you might find helpful are:
<a href="http://searchsqlserver.techtarget.com/tip/0,289483,sid87_gci1316780,00.html">SQL Server memory configurations for procedure cache and buffer cache</a>
<a href="http://searchsqlserver.techtarget.com/tip/0,289483,sid87_gci1262122,00.html">Optimize disk configuration in SQL Server</a>
<a href="http://searchsqlserver.techtarget.com/tip/0,289483,sid87_gci1307255,00.html">SQL Server tempdb best practices increase performance</a>