sp caster level question

[13xvainwarx13]

if you add class levels to a monster with spell-like abilities does it's caster level for those abilities increase with the added HD from the class levels or does the caster level stay the same?

[eggs]

"For creatures with spell-like abilities, a designated caster level defines how difficult it is to dispel their spell-like effects and to define any level-dependent variables (such as range and duration) the abilities might have. The creature’s caster level never affects which spell-like abilities the creature has; sometimes the given caster level is lower than the level a spellcasting character would need to cast the spell of the same name. If no caster level is specified, the caster level is equal to the creature’s Hit Dice."
Unless this has been clarified elsewhere, this means:
If a monster has a specified caster level for its SLA, that caster level WILL NOT change with extra HD from class levels.
If a monster has no specified caster level for its SLA, that caster level WILL change with extra HD from class levels

[ericgrau]

One trick if you want to advance SLAs are the quicken SLA and empower SLA feats. They have hit dice prerequisites and HD = monster HD + class HD.

But eggs got it right.