Present annual world energy consumption is about equal to the annihilation energy of 4 tons of matter.
Above all, I would not expect a wise race, at great expense, to set loose an army of self-replicating robots.
The sun and its retinue of planets drift as a group through the vast gulfs of space that separate the stars.
If interstellar travel is as time- or energy- demanding as the above figures indicate, it is far from obvious what the motive for colonization might be.
It would be a pity if, frustrated by the price of travel, we elected to become a society that never made contact, that never gave SETI a fair chance.