I think the 2 belts will do nicely. Problem is that you may happen 2 pairs of gloves of necropolis, which will be a problem, as you will be able to equip only 1 of those. But in any case, until then, +6 mana per turn will win almost every battle for you if you invested in higher magic already - that's flaming arrow+poison skull (targeting a stack with both post-effects is the best option) without hurting your mana reserve a lot.
+14 will be worth it later on, when you get geyser, death star, armageddon, and such.
__________________
|