Starting Void Staff instead of Morellonomicon

So since Athene's cost was increased, morellonomicon has been the better choice item because cost. I loved the mana regen on Athene's but morellonomicon doesnt have near as good mana regen, so I was wondering if going void staff would be more efficient since it is slightly less gold has 10 less ap than morellonomicon, but has 35% magic pen. And to simple it down can Void Staff be viable to morellonomicon as it would maybe give more damage with the % magic pen, since i dont like the mana regen on morellonomicon.