Don't loose too much sleep over it. It is still not clear if this issue is rod knock or just normal operation. I have over 31000 miles and little horsey is still going strong LOL. I might just be noticing more because it has gotten warmer here, and the sound is louder the warmer the engine is.
I have found that on a warm engine, the computer runs at an aggressive 48* timing advance in the RPM range where the knock happens. When the engine is cold it pulls back timing so the catalyst warms up faster. Also, these cars have knock sensors, so I would expect the check engine light to turn on if the engine did have a mechanical knock.