I would like just a single box to be running everything for the extranet. SQL Server 05 could be substituted with SQL Server Express, I guess, if it is less memory hungry.
Exchange will only be powering the company staff mails and will only be available by POP3/SMTP/OWA. Maybe mobile compatability but would only be testing at first.
The reason I ask is I can get a box of that spec for £200 right now so if it would do the job, I may as well just jump on that offer