Based on specs alone, I'd recommend you try this unit out first before buying if possible...There's just too many questions left unanswered looking at specs alone to tell if this $150 investment would yield worthwhile results.
I'm not familiar with that sub, but, if it can give you reasonable bass output into the high 20 Hz region, it could lift a considerable burden off your speakers, which probably roll-off much higher than 35 Hz...you might notice a slight improvment in the midrange of your Athenas by relieving them of the bass frequencies.
You won't know until you try...