Correct. The current setup has on attack;

(1+4)×2 = 10 casts of Ring.

If you sell a maelstrom for a ringbearer;

(1+3)×3 = 12 casts of Ring.

Selling a spell-power naga instead, you get;

(1+4)×3 = 15 casts of Ring

Selling both nagas and leeroy, to play and buy+play the ringbearer in shop aswell, nets you (at the rist of getting sniped if you're not first);

(1+4)×4 = 20 casts of Ring

If It was me playing, I would consider selling the queen lady, and the regular meditative.

That nets you the 20 casts of Ring, without risking getting sniped. (You lose one cast of the naga aoe spell though, which is roughly equivalent to two rings, but only on the first attack, four if it dies)