I recently have aquired a Lumin X1 and have connected via optical fiber converted by etherRegen from copper. My server currently is a SonicTransporter i5 CDR. From the Lumin X1 I have Triode Wire XLR's into a Vinnie Rossi L2 Statement DHT preamp. I am also trialing Qobuz. I have Roon and have experimented with Lumin App with an iPad. Previously I had only been using my music stored on the SonicTransporter. For DACs, I have the X1, the L2 DAC in my Vinnie Rossi, a PS Audio DirectStream, and a Luxman D-06. Yep, I will be reducing the herd of DACS. My previous preference has been the Vinnie Rossi L2 2.0 DAC, though have enjoyed the other two as well. I am using a microRendu 2.8 prior to the VR L2 2.0 DAC from the etherRegen for comparison. The DirectStream has been very easy to implement, and the periodic software updates have been simple and interesting to try.
The Lumin X1 is still early on playing. I had read that it takes 400 hours to reach its potential. I am glad I was aware, because out ot the box, sound quality was not up to the others. I have maybe 150 hours on the X1 now, and sound quality has dramatically improved. Last weekend I did some back and forth listening between my L2 VR DAC vs the Lumin X1. I still preferred the VR from that listening comparison, but it is much closer than prior. If even subtle improvements keep developing on the X1, I expect it to be my favorite.
I really like the simplicity of connections with the Lumin X1 and Roon integration of Qobuz and my stored music. My preference with the other DACs has been native sample rate to the DAC. The VR DAC 2.0 has an upsample minimal phase upsample ablity to 768 kHz but I have preferred the NOS (non-oversampling setting). I have tried experimenting with Roon upsampling and a short test of HQPlayer upsampling, but the i5 SonicTransporter lacks capability to reliably process very high sample rates without buffering and stalling. The Lumin X1 and my VR can accept and play up to 768 kHz and 512 DSD fed to them. I have curiousity about this, but am reluctant to embark on whole new server just for this without better knowledge of whether I would use after all. Innuos has many fans and I have mused about the line often. The lack of ability to upsample is something I wish were different, but then again, I have not done so in my limited experience to date.
I admit to some curiousity on the SonicTransporter i9 Optical that has fiber optic output (through built-in Sonore Optical Module). The SGM Extreme has optical as well, but pricing on it is well over $20,000. I suspect we will see other servers add optical fiber outputs and hope to consider those options when they come out.
The Lumin X1 has some upsample capability, but again have so far preferred native input resolution. However, I am experimenting with upsampling to 24-bit over 16-bit through the Lumin and have so far liked doing it.
Regarding which is more important--source/server vs DAC, my opinion is that both matter and are overall system dependent for results. I think a far separation in quality of either limits the final result, but feel the source/server with connection chain to the DAC to potentially be the bigger influencer.