Where should I go from here with my digital front end?

Lowered noise floor is likely the first thing one will notice with insertion of fiber, this will generally be an objective  finding. If one is comparing to an optimal ethernet setup it may be difficult to discern a difference here. With my present streaming setup I can have both optimzed fiber and ethernet chain. At present I'm most enjoying optimized ethernet from ISP through streamer ethernet output to Sonore OpticalModule, so fiber from the module to dedicated streamer(OpticalRendu). Full ethernet chain using custom streamer minus the Sonore fiber components not quite up to the fiber setup. I have one further ethernet upgrade available to me that could change the equation.

At this point, based on my own experience and many others, I'd suggest both routes are capable of delivering a top flight streaming experience. One should evaluate comparative reviews of these two modes with a critical eye. One will find vast majority of these comparisons  between optimized and non-optimized modes of bit transmission.

@emil LOL

Glad to hear it made a difference. The drop in the noise floor is in line with what I experienced in my system as well. 
Now you can add a better Ethernet cable like that Purist I mentioned or another good cable of your choice and take it to the next level. The Purist May rebalance the bass to a degree. It’s one of its strengths. 

sns

Lowered noise floor is likely the first thing one will notice with insertion of fiber, this will generally be an objective  finding.

While many cite a lower noise floor with fiber, they usually do so by saying the noise isn't noticeable until it's gone. So it's interesting you've found a way to establish that objectively. Did you do that through measurement, @sns?

So I have a Lumin d1 and was told that it has galvanic isolation so a Eno filter is not needed. Any comments?

@cleeds  Actually,  I recall seeing  noise measurements ethernet vs fiber somwhere, was cited by post on some thread here. My use of objective was directed towards near universal consensus of individuals hearing lower noise floor with fiber. I also alluded to possibility they may not hear this vs optimized ethernet.

My own experience points to variable outcomes. I tried fiber conversion prior to streamer, found it inferior to ethernet. Even greater benefit was derived from a JCAT net card XE in my ATX/Windows based motherboard custom steamer. Serves same purpose as Network Acoustics Muon.