I'm laying out a web portal for five small towns.  Features depend on server resources needed - I don't want to build something that is going to take a whole data center to run. So I have some questions:

Hard drives - are smaller hard drives that much faster?  For instance, say you are going to run a raid (mirrored) system - will 1tb drives cause a performance issue over 200gb drives?  What about the Western Digital 10k drives - are they dependable enough?  Is the performance advantage of 10k great enough to justify cost?

Processors - of the software components in a DNN site which ones are threaded and can take advantage of a multi-core processor?  What are the advantages of a multi-core processor  in a DNN install??  Do quad-cores offer that much advantage over a dual core in a DNN install?  Then you have the multi-processor issue - if you have two quad-core processors what determines which processes get sent to which processor?

Get lots of RAM.  When I look at my processes, each DNN instance conusmes a great deal of RAM.  This is configurable in IIS, but just like all apps, the more RAM you have, the better. I found when I ran low on RAM DNN AppPools would recycle much more often and reliability and speed were affected.  I run 8-GBs of RAM in both my servers but I run many sites.

For HD size, What I have found in RAID is that if you have a huge drive, the RAID takes forever rebuild.  I wanted to run 3-500 gig drives in a RAID-5 where one drive would be redundant and I would have 1-TB in space.  When I ran the server it would take about 2 days to build the array and if Windows crashed, the array would rebuild again.  When it was rebuilding, the server was so slow it was in effect useless.  I ended up using 2-500 GB drives in RAID-1 and this solved my rebuild issue.  The array would rebuild in a few hours and performance was ok duing that time.

Hope this helps.