Best bang for buck integrated amp for $500

I wondered how the Rega IO would compare to the Keces E40 I have. Essentially the Keces outputs similar watts but a measurement I found showed at a fairly nice distortion curve. It is also stated to be able to output up to 15 amps which if true shows some decent design.
I find its’ bass output substantial, tight and fairly layered. The stage depth isn’t flat, there some dimensional to it. I think you stated the dac wasn’t up to par and I cannot attest to that however one reviewer found it quite capable and competitive as to audio quality even though it doesn’t do more than cd quality. Same with the phono stage, ancillary but capable. Plus, it has a pre out.
The sound quality is what I was apprehensive about because there are no returns on the purchase. But the Soundnews review was IMO, accurate. It doesn’t quite give those wispy, super airy highs but the highs that are produced are musical and have body/weight to them.

The tonality reminds me of my Hegel h160 to the point that if I were to AB test both amps for someone not familiar with them, they probably couldn’t tell the difference.

Still, someone will eventually do a comparison of these smaller amps. If you listen at moderate volumes, you may find you’ve found a unicorn.

Well guys i have decided to part with the REGA IO, i have listed if for sale on ebay.  Im moving on from this amp if your interested in buy send me a message.  It like new no more than 20 hours on it, no marks, scratches and comes with box and remote.

I've carefully read and re-read your posts regarding your experience with the IO.  Not sure, but doesn't bass need a bit of room to fully spread out?  If your up close to the speakers as in a desktop setup, it might sound like less bass than if you are further away.  The upper mids and highs might be grabbing your attention more than the bass, perhaps?
The reviews from alpha-audio.net state this about both the E40 and the Io:
Keces E40: What immediately strikes you is the exceptional low-end that this amplifier sends through our speaker. We have seldom heard so much power and control from such a small box. The Rega Brio is the closest but the Keces E40 goes far beyond… Bizarre. A lot of modern monitors can use a kick in the butt, but of course it’s important to keep an eye on them. With our little Cabasse Surf mini-monitors it was sometimes too much of a good thing. 
Rega IO: Coincidentally, we ourselves have a fine, modest amplifier in our listening room! It’s the Keces E40 (599 euros) which, as its name suggests, has 40 watts in class A / B on board and also performs a bit above its level. It even delivers some decent watts in pure class A. And it offers, besides a phono stage, also a USB dac. So there are more similarities than differences between both amplifiers. But in terms of sound we notice some nuances here and there. The io has a more powerful bass and is a bit more playful than the Keces. The Keces is a bit more balanced to our feeling but a bit less transparent. Choices, choices, choices. 
I know how most of us feel about reviews, alpha audio says the Keces e40 goes beyond the Brio but says the IO has more bass than the Keces but suggests it's less than the Brio?  Kind of doesn't make sense.
The Keces has some kick like no other amp I've tried under a grand has but it's also smooth. I think the IO adds a bit to the upper mids and treble which if not balanced with the lower mids and bass will stand out to much so all you'll focus on is the brightness/clarity at the expense of bass (SoundArtisit SA-200A did that, way too bright in my system).
Are you jumping the gun selling off the equipment too soon because you are frustrated?  I might have jumped on the Triangles but I have the Zetas which have a titanium tweeter.  Not sure about the softdome.
As to the amp, I am very tempted.  It may give a bit more aire on the upper mids and treble but if the energy is too much, it might overshadow the lows. The Keces doesn't have quite the aire of the Emotiva A400z which was way more powerful than the BasX A100 but I liked the high frequency extenstion, but overall it didn't sound like a higher end product. The lows were a bit less, less defined and overall the SS was very 2 dimensional.
Maybe your jumping the gun.  Give it time for your brain to adjust too.  Unless you just hate your system, keeping it intact will allow you focus on what you like or need and when you do get something else, the comparisons will be more useful when you swap equipment in and out. 

Something to think about as I know how frustrating one can get from experience regarding audio.

I have moved on from Rega IO, i dont think im jumping the gun.  Way harder than i thought it would be.  Looking at other options.

Former owner of many compact amps. Here is my compact amp ranking.

1. Burson Funk with Vivid OP amp upgrade - Great bass, warmth, and clarity. This amp is a unicorn.
2. Rega Brio R - Exciting forward sound, unrefined treble, high noise floor, good tone...enjoyable. 
3. Emotiva Bass X 100 - Great build and power for the money. Average across the board for sound...pretty neutral sounding. Brio R has better tone and is just more engaging.   
4. Audioengine N22 - Good mids and pleasant treble. weak bass. warmer timbre. sound lacks dimension, body, and bite.
5. Parasound Zamp V.3 - Tonally cool. Felt like much less than 45 watts. Bad harmonics. 
6. Ice Power 125ASX2 - Sounded like bad Class D. Great bass and bass grip. Mids and treble were very unnatural. thin, cool, dry sounding amp. Would be good for home theatre.