Well what is says on the box is the minimum to get it to run. Obviously it's going to perform better on a quad core machine than it would on a dual core.
Dual Core and 4Gb of ram will be enough, until it isn't.
In other words 'Will my car win a race?' is a fair analogy. It all comes down to how much you intend to do. It is possible to make track that is too complex for even the fastest computers to play back in real time. It is also possible to work around not having enough processing power by bouncing your output down to audio tracks and removing the original devices - sub-mixes within your mix can free up a lot of processing power but put more strain on your disc read speed.
In short, get the fastest computer you can afford and reason will find a use for all that power if you want it to.
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