I can’t speak to the Zen, but I have been running the i5 with UltraRendu for over a year. Terrific support from SGC. Coupled with Roon and Qobuz, my biggest problem is finding enough time to listen to all that I would like to hear. I skipped dBPoweramp and just use the ripping software in the i5 with a cheap DVD drive. I did add an Ultradigital from Sonare so I could use the I2S input of my Denafrips Pontus II. I use my laptop and an android tablet as interfaces. I bought an internal 4 GB SSD from B&H and it works flawlessly. I will admit that I used the Roon DSP to smooth out a little roughness in the upper mid/lower treble range. But this has lessened over time. Updates usually run smoothly, although a second reboot of the i5 is often needed, and you should keep the Roon app on your tablet or laptop up to date.
I use free metadata software to manage the files and keep everything easy to find. MP3tag works great for me.
Backup to my WD portable 4GB USB drive is easy and fast...I keep a USB cable plugged into the i5 and dangling around to the front. Connect the drive, open the Sonic Orbiter GUI, and start the backup. USB 3 is much faster than the 2. The only thing that takes a while is adding album art to my music files. Faster home network speeds help with this. I added a cheap Ethernet adapter to my laptop to avoid the WiFi, and it sped things up considerably.
Overall, I am happy, even if my rack looks like a Rube Goldberg contraption, with a bunch of little boxes, power supplies and cables.
I like the simplicity of the Zen, but it’s hard to imagine better support than you get from Andrew at SGC, and like yourself, the i5 bundle was clearly the most cost effective way to get hi res files, Roon and Qobuz to all work together seamlessly.