just tried Neutrino for fun. Can't recommend it on sound quality versus Play or Pure Music. Sounds muted and a bit fuzzy. Of course, it's got tons of effects if you need those, so it's really a different kind of app - more for production than playback.
Actually, having switched back and forth amongst all these various options for a while now, I've come to realize that I'm not such a fan of crossfeed afterall.
Maybe if I still had the 112db Redline monitor, I'd feel differently - I liked that - but after the trial period ended, I didn't cough up the $100 for it, and decided to go with the $10 Canz 3D instead. It's ok - for some tracks, I like it. But the more I play with it, the more I realize that the effects it's giving are coming at cost of different forms of detail that it takes away. And while the reverb adds a certain spatiality to the sound, it takes away the spatiality of the original L/R, which might not sound like it's supposed to through speakers, but it does sound better than the blending through CanZ.
My recommendation would be to go with PLAY and CanZ3d if you want to mess around with crossfeed and see if you like it. Only $10 total. Without Canz, Play is quite good.
For overall sound quality though, I haven't found anything that beats Pure Music and it's only about $130. But there's a free demo. It's perfectly integrated with itunes. It's a keeper for me.
***UPDATE***
I just downloaded the latest update from Amarra, and I'm blown away. Wow. I'm not 100% sure, there are little differences, but I'm pretty certain I can say that even the Amarra Mini beats Pure Music. The bass definition and size and clarity is just astounding, and the rest of the spectrum is tight and controlled, airy, just very, very nice. Ah, but I see it is $270 or twice the price of Pure Music. Hmm. Off to test the Jr version for $79.
new update -
well, that didn't take that long. The Amarra Jr version is CLEARLY INFERIOR to the Amarra Mini. What a shock - their $79 product is not as good as their $270 product. But somehow I was hoping it would be, because I'm not going to be spending $270 anytime soon.
Going between Amarra Jr and Pure Music, it's also no contest - PURE MUSIC BY A MILE. So what we've got it capitalism at it's finest: you get what you pay for. $79 amarra jr is worst, $130 pure music is MUCH better, $270 amarra mini is about the same as Pure Music, maybe a tiny bit better, and who cares about Amarra full at $700? Probably best of all, but I'm not buying it.
So I'd recommend that anyone who hasn't tried anything but iTunes, do yourself a favor and get PLAY - it's free, and it's a million times better than itunes. But if you're willing to spend some money, skip Amarra Jr and get Pure Music for the $50 more. It's MUCH better. If you've got the money for more than that, you can test for yourself