Huh? My personal Modpacks do run fine on a Quadcore Celeron and eight gigs of ram. Sure it takes like 15 minutes to actually start minecraft on that particular Machine with a heavy Modpack, but it works.
And Servers dont have the restrictions of rendering Stuff at the same time, so they are more lightweight than that generally.
The only REAL issue is Players that find a fun new exploit that lags the Server to shit, or a Chicken Farm. Luckily the Chicken Farm issue is something i fixed back in GT5, so that is a nonissue now, heck Mojang even copied the entity cramming mechanic i invented. XD