This is a really late answer to your question, but yes. It powers the HE-500 very well. In fact, it powers the HE-4 incredibly well also. After writing up a comparison between the HE-400, HE-500 and HE-4 over at HF, I got in a debate with someone who claimed that Ember was not a sufficient amp for the HE-4 (not enough "power"). While I hadn't heard any other amp that could power them as well, I didn't have much at my disposal anyway. So, per many users' recommendations, I bought the Emotiva mini speaker amp to test it out on the HE-4. This amp has unarguably enough power for these puppies.

Well, I got the amp today and while it does power the HE-4's very well, I'm unimpressed when comparing it to Project Ember. Ember significantly better job separating instruments while still having just as much punch (this is on Ember's lowest output resistance setting). This little guy is a powerhouse, and that doesn't even take into consideration the amount of possible configurations (between gain adjustment, tubes, and output impedance).

Solderdude, if you would be willing to help me out here, I'm a little lost at understanding why this amp is so impressive. My ears are telling me, based on my comparison today, that power is indeed not everything. Over at HF, it's constantly a quest to find an amp with the highest wattage output for one's set of planar headphones, and I don't know what to say other than "power isn't everything". But if power isn't everything, what are the other pieces of the pie that are contributing to headphone performance?

EDIT: I just saw your new thread, I'll check that out first...

By power amp, you just mean an amp with a focus towards high power output?

Man, I swear. If I could buy a shit-rake, I'd be raking through HF threads like a mad man. I barely have enough patience to keep up with all the equipment switching. I'm thankful that this site has done a significant amount of shit-raking for me.

Cool. I guess ultimately, still, it just comes down to personal preference. Have you had a chance to listen to Ember? Or the HE-4 for that matter? It looks like if Luis can't find his HE-4, I may end up sending you another package of stuff to play with.

Finally got a chance to audition the Ember, thanks to Thujone.

First off, Jeremy over at garage amps is fantastic.  When the amp arrived at my house it had a damaged power switch (thanks USPS).  Jeremy sent me a pre-paid shipping label and had the thing back to me in under a week, fully fixed and ready to go.

My chain has been Modi 2 U --> Vali --> HE-500.  With the Ember, the majority of my listening was done with the stock tube.  It reminded me of the Vali in that you could certainly tell you were listening to a tube amp, but not in a syrupy/smeared sort of way. 

I've always enjoyed the 500s...first from my Asgard, and then from the Vali.  I still maintain that the Vali is a good match for them.  That said, the power provided by the Ember takes them to another level.  In short, it grabs the 500s by the balls and makes them sing.  Ample power, while still retaining a very clean/refined sound. 

When I first received the amp, it was set to medium impedance and low gain.  I had to get to about 12 oclock on the volume dial to get to a place I liked.  And, while it was good, I wasn't blown away.  It was a step up from the Vali in terms of clarity.  I could hear deeper into recordings and notice a lot more tiny detail than I could with the Vali.  But, at nearly 3x the price?  That was a tough sell for me.

After contacting Jeremy, though, he recommended low impedance and high gain.  That did it.  More authority in the bass, more drum impact, driving guitars...all the good stuff.  And still, it sounded clean, polished, and refined.  My only complaint here is that there wasn't enough play with the volume...9 oclock was pretty much it.  11 oclock on really uncompressed music...classical, choral, etc.  Apparently one of the features of the new Ember 2 is the ability to readjust the volume knob range via an input attenuation module.  Pretty awesome feature.

Speaking of customizable, you can also adjust the impedance as I mentioned earlier, the gain, and whether or not you want to bypass the input caps for a purer signal.  All of these settings can be changed on the fly without turning off the amp, which makes A/B listening very easy to do.  And, while it has nothing to do with sound, you can also change the color of the LED under the tube, or just turn it off completely. 

These all worked well.  I plugged in my DT1350s, and of course had tons of hiss due to the high gain/low impedance.  So, I switched to high impedance/low gain, and the 1350s sounded great.  There was still not a pure black background, but the background noise was barely audible with the music paused.  Already an advantage over the Vali, which doesn't play nicely with those particular headphones.

The cap bypass feature was interesting.  It may be placebo, but the sound did seem to improve when the caps were bypassed.  Sadly, though, the volume knob became very noisy when adjusting the volume which caused me to go back to using the input caps.  According to Jeremy, this can be very tube dependent with some being far noisier than others.  There was also a little scratching with my 1350s by the way, even when going through the input caps.   

All in all, the Ember is now on my list.  Once I save up the cash, I plan to add it to my lineup.  I wish I had a pair of 250-300 ohm headphones to try on them, but I have to imagine they would sound fantastic with all of the tuning options that the Ember provides.  I'm looking forward to hearing more impressions from more experienced ears.  It's a real shame there isn't more talk of these amps.  Here's hoping that will change soon.

RE, what's the value add IYO that Ember 2 has by way of some of the new features against Ember 1 ? I bypassed the input caps but do not get any scratching. My tube is the Amperex Golden Globe.