A good place to get started is http://community.landesk.com/support/docs/DOC-6459
For what LANDesk can do, it makes sense to make it fly, but doesn't mean you need to chuck HW at it.
Kit is relativity cheap at the moment.
and my own experience is:
4 / 8 core processor
12 GB ram (Min)
RAID 5 for the install, keep C:\ as clean as possible
DB could be on it's own server, but with only 400 devices should be ok on the raid, but it does depend upon what you are doing with LANDesk
Heavy data like, Patch, Software packages etc can be off core on another server.
A lot can be done with Hyper-v around cluster, priority etc.
Hope this gives you something to go on.