You should stay within the avid specs for performance and longer life of your machine.
If you build your own system better not build the lowest level. New software changes and development will require more computing power by all softwares (avid, adobe etc.)
Also, make sure you can upgrade components if needed.
I build a Pc in 2008, it is still running and was good for using Avid for about 5 years.
Ronen