[3.5e] Starlock - planning 6th level.

[Adumbration]

As my kenku starlock - warlock re-fluffed - is approaching 6th level, I'm faced with a dilemma. Two problems, in fact. What feat to take and which invocation to pick?

Feats so far:
1st: Spirit sense (HoH)
3rd: Knowledge Devotion (CC)
Flaw: Greater Resiliency
Flaw (Noncombatant)

Invocations so far:
Entropic Warding (handy)
Otherworldly whispers (fuel for Knowledge Devotion)
Eldritch spear (helps with distant enemies)

The problem lies mostly with the feat. The DM has promised that I can take Supernatural Transformation for my Eldritch Blast at level 9. So far so good. The problem is with the benefit; it makes it supernatural ability, and thus if I now chose Maximize Spell-like ability, it wouldn't apply later on. Should I pick some other feat at 6th level, such as Extra Invocation, instead of Maximize SP-ability, and get Supernatural Transformation later on, or go for the spell-like ability feats?

What Lesser Invocation should I take? If I take Extra Invocation, what Least invocation should I get?

Character in full here:
http://www.thetangledweb.net/forums/....php?cid=20052

Most books available, except for campaign specific stuff and Magic Item compedium, plus possibly some that I've simply forgotten about.

[Lert, A.]

Should I pick some other feat at 6th level, such as Extra Invocation, instead of Maximize SP-ability, and get Supernatural Transformation later on, or go for the spell-like ability feats?

I'd stick with the SLA feats.

What Lesser Invocation should I take?

I like Voracious Dispelling - debuff enemies and hurt them at the same time. At will. Works best if you have high DCs for your invocations, naturally.

If I take Extra Invocation, what Least invocation should I get?

If you take this route - not recommended since it will become pretty useless in a few levels - you should have either Baleful Utterance or Summon Swarm.