My magus has Magical Lineage (Shocking Grasp) and Intensified Spell. My magus can cast a Shocking Grasp with a 1 level spell slot up to 10CL.
At level 6, I chose the magus arcana Empowered Magic (Su):
The magus can cast one spell per day as if it were modified by the Empower Spell feat. This does not increase the casting time or the level of the spell.
I can Shocking grasp at 6d6+3d6 once a day in a 1 level spell slot
At Level 7, I picked the feat Empower Spell (Metamagic).
I can Shocking Grasp at 7d6+3d6 in a 3 level spell slot.
Also, can I use both together? If so, will it be 7d6+3d6+3d6 (7d6+7d6*0.5+7d6*0.5) or 7d6+3d6+5d6 ((7d6+7d6*0.5)*0.5) in a 3 level spell slot once a day?
I know about the multiple metamagic feats on a spell:
Multiple Metamagic Feats on a Spell: A spellcaster can apply multiple metamagic feats to a single spell. Changes to its level are cumulative. You can’t apply the same metamagic feat more than once to a single spell.
In my case, I am not sure this rule will disallow to use both together or not. The arcana is not the feat, but the arcana apply the same effect. Note that the metamagic feat apply at preparation time and the arcana at casting time (but I am not sure that it will matter).
Can I use both the arcana Empowered Magic (Su) and the Empower Spell (Metamagic) on one spell?