I've enchanted a ring, necklace, and apron to each give me a 20% bonus to smithing which is already at 100. On top of that, I have some blacksmith elixirs that give a 50% smithing bonus. Using all these items at the smithing wheel, I've been able to improve my ebony greatword and war hammer to legendary status without the perk that allows me to craft ebony armor and improve it twice as much. The damage output on these weapons is pretty nice.
I've been grinding like mad to get the four perks I need to get to advanced ebony smithing, but then I got to thinking: When I do get that perk, will I experience even higher damage/armor ratings when improving ebony gear or am I pretty much able to use my magical items to augment my smithing ability as far as the game will allow?