Questions about SQL server hardware config

Hey guys,

I have been developing a SQL based data warehouse for financial reporting purposes. I do expect the database to continue to grow over the next few years.

Right now, I am running SQL Server 2000 on an HP DL380 G3 with dual Xeon 2.8GHz, 1.5GB of ECC DDR RAM, 4x 300GB SCSI 10K RPM HDD's.

I would like to replace the server as it is now two generations old and because when there are five people running queries against the data, it starts taking minutes to return the results. When this reporting database hits production, it will be queried by up to 20 people simultaneously and I don't feel the current server will provide results in reasonable amounts of time.

I would like to know what you people think I should be doing to provide an optimal environment for this data warehouse. Should I stick with SQL Server 2000 or move to 2005? Why would you recommend that?

I am thinking of replacing the server with the following configuration: HP GL380 G5, 2x Xeon E5345 Quad-core CPU's, 4GB PC2-5300 ECC DDR2 RAM, 8x 72GB SAS 15K RPM HDD's. Do you think this is an ideal configuration? Too much? Too little?

I would love to hear what you have to say and suggest. Thank you in advance!

Chris.