Help me build a system to 7box EvE and 4box D3

I am looking for some advice on how to upgrade(rather:/create a new) system to run 7 EvE clients at the same time on one machine.
Furthermore I°d like to run D3 on 4 clients from time to time.

Do you guys have any advice for a solid, but not too expensive system that I should aim for?

Any advice on minimum and optimal specs is highly appreciated!

[Alge]

You may find or get an answer here: http://www.dual-boxing.com/forums/29-Hardware-Tools