Your question doesnt really make much sense. No one races ships are really more 'powerful' since all races share the same basic tech lines far as weapons go. Its really a question of how advanced you are, not what race you are. I play human all the time and who has the most powerful warships?....I do! But this has more to do with the fact, I try to conquer planets with other races shrinkers and built ships on worlds with Ship Quality and HP bonuses. IoW, I try to leverage every little advantage the game offers. The AI just builds just does it usual cheating and canned designs. 

And you can acquire the Acerans Planetary defence easily enough. Its quite buy-able\tradeable, as are all the planetary defence techs that other races own. Its not an alignment tech.

Thanks for the responses, people!

I was just wondering if a particular race had a "racial" technology" that gave better ship weapons and defenses than those available with a "maxed out" Terran tech tree. I could have phrased my title better (sorry!)

So, no Dread Lord ships (not surprised). Is there any way to get precursor rangers?

Thanks for the note about "war of the gods". I'll check it out.

May I assume the way the other empires get them is from random events?

Good to know. That should do it.