I like destructor or embolden more than enhance for storm guardians with enhance they become ok at melee but the low str and bad armor save balance it out. The extra flamer does more for me ( give it a try though you might like it ). I like them in a waveserpent with brightlances also, I run several units just like that in my current main list.
I do feel a bit bad if I made you drop the spears they can be truely amazing or truely terrible and don't need the autarch to be a worth while unit. They drive me crazy for five straight games and I start thinking that they don't belong in any type of list only to have them come through with truely game changing charges that renew my faith in them. They are the glass cannon of the eldar ( well most of the army is but they get my nod as number 1 ) the low model count can mean a few bad rolls cripple them but they have speed and power in spades. People will say that they are not worth the cost or to fragile or dead if they get charged ( possibly all true ) but well used or with a bit of luck they do preform, there is a reason why they are feared and targeted by my friends after all
guess I'm saying you might want to play a few games with proxies or something before simply dumping them. But I can't fault your replacement units.