I’m writing this as an answer to @Eskamobob1 reply to my question in Luxury Precision P6 Pro because it ends up being about the Cayin C9 and maybe also other C9 owners can give their opinion on it.
I mirror @GoldenSound impressions. The p6p is a super incredible dap and even straight dac. Tbh, I think you end up loosing a very significantly level of sound quality using a C9 even. Unfortunately it’s USB performance is seriously sub par for some reason loosing out even to LDAC bt in (with local storage on device being best Sq imo).
Outside of the p6p, lpgt and sp3k will also both be very solid option. L&P will also be dropping a new dap that apparently solves the interface and USB problems in the next month or so that may be worth a look.
Honestly though, I would personally recommend realy thinking about why you want the c9. Quite frankly, there isn’t a single use case that I wouldn’t take a different portable setup over one using it. It isn’t as powerful or commanding sounding as the spec implies, the technicalities are pretty lacking compared to others at the price. I think the best pairing I heard it with was p6p into utopia on class a tube but I would honestly way rather have an sp2k or lpgt for utopia alone from an Sq and synergy perspective.
Why I want the C9: I already own one 
I do have the utopia and I kind like the C9 with it. I know you compared it to a lot of other portable daps and amps, I can’t say how well it fares with others. But on the technicalities and with the only three sources I could pair it with (ak acro ca1000, moondrop moonriver 2 and xduuo xd05 bal) I am totally fine with it, actually it is better than what I get with them as a dac/amp.
I know this could be because they are not in the same league of the daps you were talking, but specifically on the sp2k and sp3k that you consider as better options, I do own the AK Acro CA1000, which is possibly in the same level of the others. With deezer app installed on it, it had a good hollographic presentation and was very dynamic, but the soundstage was very narrow (and crosfeed just makes everything else worse enough for me to prefer not using it to fix this problem). I think this problem could be deezer specific. When feeding it with usbc or usbc to coax or optical (this one from TV), soundstage problem is gone, but the two good things I mentioned are also not there. It is very good still and in the same league of the C9 itself. But my preference ab testing it against the C9 + xduuo xd05 bal as a dac always lead me to the second option, except for one song. [Also I have to say utopia 3.5mm cable with the adapter out of the 6.35mm output of acro ca1000 had a really good textured/tactile bass that was the greatest bass experience I had, but my cable broke after some hours of use, my dealer is getting me a replacement. On its own XLR cable or the ones I got I never got the same bass].
I had owned a GSX mini just because I’ve always been interested in it. It was more detailed than C9, but not in a level that I think I lose anything out of the C9. Soundstage yes, this could be a selling point of it, it is huge. Cayin C9 is noticeably better than using xd05 bal, but it is still very close. The thing is, the larger GSX mini soundstage came with a less tactile, more ethereal sound. I do not necessarily prefer one over the other, but in this case specifically I do prefer the C9. And C9 bass is also better than mini, but it is yet in the level that I still crave for better texture, it is more of an undefined rumble. Gsx Mini also could make Utopia sound too bright in a way I see many people complaining.
What I think C9 is not great is that I feel it a little darker sounding and vocals are good, but when ab testing against xduuo xd05 bal, I prefer xduuo, there I would like to see a little more of sweetness.
Its selling point soundwise and why I do want to try a better dac in it before maybe trying better desktop [I do also value transportability a lot, but just talking sound]}] option is the presentation. How well it places the things inside the soundstage allied with instrument separation and how bigger it makes each instrument (or singer) [not soundstage] is something I never heard either out of acro ca1000 or gsx-mini or when I had an violectric V200 with hd800 and fostex th-900 in the past.
That is why I’m looking a (portable) dac for it. Xduoo XD-05 bal is doing a great job, but I’m still eager to try better options. LP P6 Pro is way out of my intended budget, but I just looked at it because it seemed an endgame dac for me personally (which was discarded). For know, what I think I should consider in the market is:
DAPs: I’m avoiding this route. I see most daps as good in the SQ department, but you see implementation problems either in hardware or interface. I do not discard going this way, but I am waay more cautious before trying it. Also, I won’t use local files, so I would be overpaying for screen and other things. But, it seems that the totl daps are one of the few options out there with dedicated 4.4mm line out, which is something I believe will make a difference, and that sound closer to desktop units.
Dac/amp combos: I have eyes on both Earmen Angel or Ifi Diablo, but I do feel it is like buying something that most of its price tag comes from the amp section.
Chord hugo 2 is the highest contender by now, as some utopia users gave positive comments on it with utopia, so there is a dac I could test with the c9 or a dac/amp that could potentially even replace the C9. It is single ended though and the micro usb data and charging inputs are for me major drawbacks. And maybe it is worth waiting for when they bring a new version as it is quite old compared to other options, who knows.
Dacs: maybe going with things like earmen tradutto [4.4mm out stands out] or chord qutest with a portable battery, but the problem is finding a battery… Currently I think hugo 2 is probably better than this, as the external battery is one extra thing.
I’m also thinking in maybe just buying a gustard R26 to see how much the dac of xduoo xd05 bal is leaving on the table. If is not that much, I already have a dac for a desktop amp and save money in the transportable option.