Artifact bonus to an individual spellpower will stack with artifact bonuses to Universal Spellpower, yes.

You would think after 8 fuckin thousand posts he'd figure out the basics at least ... 

It's definitely worth looking at gear sets other people post, that's where I learned about this a while back.

Do you have Isle of Dread? Thats got some interesting options, though it generally means going through a whole painful gear Tetris session rather than slotting a few items in.

You probably looked at all this but I like the below. To be fair my fire sorc is an alt on a second account and I have limited items already slotted with LGS/Desert sets or notable mythic/reaper boosts so its easier for me to improve than it would be for a tooled up main.

Dread Curse five piece dread set bonus.
    +15 Profane bonus to Melee and Ranged Power
    +25 Profane bonus to Universal Spellpower
    +30 Profane Bonus to PRR
    +2 Profane bonus to Spell DC's
    +2 Profane bonus to All Ability Scores
    +3 Profane bonus to hit and damage

Notable items.

The offhand Keg with fire/force spellpower/lore and Quality CHA 3, though that blocks a few things of course. I like salt.

Pendant of Earth with Insightful Fire/Force/Acid and can slot 10 Insightful crit damage. This will probably get in the way of nice items.

Admiral Gloves Illusion Focus, Wizardry, Will Saves and can slot 20 Insightful crit damage or Charisma 15

Kopru Bracers Necro/Illusion focus, profane HP, and again can take 20 crit or cha 15.

And the artifact as you say. I quite like the sea woven belt as well, as with the manaweave armor you end up with with a nice SR (most people say SR is pointless, I like seeing the bubble pop up all the time and dislike standing around being beaten on by monsters when helpless).

3 Piece Deacon of the Auricular Sacrarium (Items boost Int though );
    +6% Artifact bonus to Universal Spell Critical Chance
    +25 Artifact bonus to Universal Spellpower
    +15% Legendary bonus to Spell Critical Damage
    +30 Bonus to Magical Resistance Rating Cap

As I say, not tried to make a set for Sorc yet. I will try to do that over the next couple of days. I made a set for caster bard over the weekend with 5 Salt, 5 Dread and 3 Walking Ancestor and that turned out well, but there's obviously no room for any other item or set.

With the Dino crafting, and the new augments I did find I could turn what was pretty much a filler item just to get a set, into something pretty good. Unlike in Fey with your Noct ring example.