The E30 well worth the money asked for it relative to the other descrete DACs on the market with similar functionality.
However, worth the money is a relative term, I don't know what's 'worth the money' to you. You have excellent amplification with the L30. It has very low noise and distortion (so low that it will be inaudible) and it has plenty of power to drive vritually any headphone you are likely to purchase. It's basically an 'end game' amp. Similiarly, the E30 could be considered as an 'end game' DAC if USB to Line out is the extent of your requirement (you don't require balanced outputs, bluetooth, etc.).
So buying an E30 could be worth it, if you accept that you'll never need to buy anything else (unless it breaks). Just don't expect it to increase your K/D ratio.