Sounds good. I believe I can still return the E30 as I got it just a couple of weeks ago.
By the way, have you compared listening to the Sonata solo versus connected to the Atom? Does the Atom actually improve the sound quality?
Second question: How do you connect the Sonata to your Atom?
A headphone amp allows you to deliver more power to your headphones and that's
all it does. You will find various pundits eager to attribute magical qualities to an external amp with oodles of power, but this is just superstition.
You need enough power to drive your headphones loud enough, more power won't bring any benefit. To calculate how much power you need there's a calculator
here. Inserting the sensitivity (104dB/V) and impedance (333ohms) of the HD650 shows that for an output of 110dB (which is really very loud) you need 12mW with 2V. The Temptotec can produce 2V and Amir's review showed it putting out 14mW into 300ohms.
It's unlikely you'd notice any difference with an external amp unless you want to drive the headphones to extreme levels. But it will provide the reassuring feeling of having spent more money. The Temptotec struggles with low-impedance headphones, which is where an extra amp can be useful.