Improved Spell Resistance

Hard nurf in 3.3 update
This enhancement line used to be way more effective than as is, but got nurfed pretty hard in 3.3 enhancement revamp. Now days it is barely taken, as SR 20 for 10 action points dosen't worth it at all, compared to SR 19 random loot (belt or ring slot), SR 22 raid loot (Ring of Thelis) or cleric Spell Resistance buff (caster level + 12 SR).