Then don't listen to anyone here... except for me.
I don't own the Solaris, but have used it quite extensively (I had a week with it, plus some other shorter sessions). Most of my observations are based on the Andromeda, but have crosschecked with the Solaris when I had the opportunity. I've used my Samsung Galaxy S8 and UAPP (yes, you read it correctly, a smartphone) as my source for months, kept A/B with expensive DAPs and barely found any differences. In the end I got an ZX300 (because I was curious to try out the Bal and my dealer doesn't carry Sony, so had to buy it) and decided to keep it because I can use it to drive my HD600 as well. I also enjoy the slightly different sound I'm getting from it with my Andromeda, but to be perfectly honest I could've gone on for a long time, completely satisfied with the S8 (the UAPP is an important component, otherwise it's quite hissy and there might be other aspects of the sound that don't excel).
So, if you really don't want to go crazy and have one of the better sounding smarphones out there, then start with that. Maybe order an zx300 from amazon, test it out and see if you really hear an improvement (I would also recommend going Bal in that case).
Bare in mind, I'm not saying a smartphone is equivalent with an expensive DAP in all situations, but in the case of the Andromeda and Solaris (very sensitive IEMs) I found them to be very close.