The more ram the better, right? Besides, onboard video uses a lot of ram. Maybe not 4gb, but a lot.
No its a complete waste, this is not a Windows platform, it just won't get used for anything other than file caching, which will not improve the performance of your system at that range! The system you described would run with 512MB at a pinch, 1GB would be plenty. If you intend to build out and have lots of MDs and HA, telephony, etc then 2GB is oodles
Well we install 4GB of ram on our biggest Core's, as at the margin on a Big system the extra performance is worth it, and the cost differential between 2GB & 4GB is pretty minimal on the overall build cost.
But I do agree with Colin that in your situation it would not make much sense... 2GB looks to be the 'sweet spot' on ram right now so you probably might as well go to Colins upper end recommendation.
All the best