Honestly, when it comes to the staff working in the computer centers, they usualy know dick about 3D graphics and redering, unless thats what they speialize in.
They just try to sell you things you dont realy need, they are the theory guys, the read a book about something or heard someone say it and then adapt it as a fact even if its complete nonsense. Fact is if its just on a hobby/entry level you have no need at all for a high spec machine.
Even a low spec rig will let you run 3ds MAX just fine.
And like i said unless your gonna do huge amounts of animation and render sequenses you will do just fine with a singel core CPU.
Its would even be better to spend the money on some 2nd hand comps and build a render farm rather than to buy a dual core if its just for rendering.