Sleep spells with a higher HD cap, What level should they be?

[Torger Miltenberger]

So sleep spells,

We all know of deep slumber. Basically it takes sleep, makes it two levels higher, reduces the range and raises the HD cap by 6.

So what level do you guys think a sleep spell with a HD cap of 15 should be?

20?

25?

Not just Sorcerer/Wizard level but Bard and Witch levels as well.

My gut reaction is

Cap of 15 should be be sor/wiz & witch 5th, Bard 4th

Cap 0f 20 should be sor/wiz & witch 7th, Bard 5th

Cap of 25 should be sor/wiz & witch 9th, Bard 6th

I'm not interested in Mythic rules. I'm aware that there's some kind of mythic deep slumber that raises the cap to 20 but my group doesn't use mythic so that's of no use to me.

Anyway I'd love to hear the community's thoughts on the matter.

- Torger

[Volaran]

Seems reasonable. The witch hex has already opened the door for sleep being an effective tactic later in the game.

[SAR101]

Those all seem reasonable, allows for a nonviolent tactic to remain useful later in the game.