It depends. Innuos is definitely at its best running Sense. It is not designed and well suited Roon. Having an external player int he Lumin helps but does not change the underlying fact.
Least Expensive Solution: The Lumin does not need to be replaced. It is serving as DAC and renderer and having those two features in one box is pretty appealing. The internal connection optimizes clocking and keeps jitter to a minimum.
Lumin has its own software that is pretty good. You can continue streaming Qobuz and Tidal through the app. I believe it also supports a direct drive but only at a modest level which means it lacks the processing power for good indexing. Probably best to offload that onto a NAS. You could get and implement a NAS for a few hundred dollars. Upside is it is inexpensive. Downside is NAS's are fidgety on the network at times and they can fail. You also have to switch to Lumen's software which I dislike personally.
Mid Priced Solution: Roon Nucleus One or Titan: The NucleusOne is like building a NUC with a mid level processor. It is best for streaming only. It can do the job for local music but not incredibly well. If you have a decent local library or you use Roon DSPs this is a bad option. The Titan is a much higher end device and I would be comfortable letting it handle up to 4TB of local data with DSPs.
Both are a bit noisy and it is best to keep them out of the room and near your router rather than your stereo. They are "transparent" as another user mentioned. I find the sound output a bit cold. This is not bad, just a fact and just needs to be accounted for.
I just did a (highly unfair) test between a Nucleus Titan ($4k) and an Anitpodes Oladra ($29K) in a customers system. We heard a radical difference. With his DAC (Meridian Ultra), the Antipodes sounded awful. It sounded like the tweeters were blown. No top end energy. Swapping in a Weiss Helios the balance was much better and sounded incredible with the Antipodes. The Weiss with the Titan was unpleasantly bright but just about perfect with the Meridian. We learned the Meridian is on the warmer side.
That was a longwinded way of saying either Roon device might be a bit brighter than your Innuos. They have a return policy. Be prepared to use it if need be.
High Priced Solution: Antipodes K41. Antipodes makes high end servers that IMO do the best job of supporting Roon. They are one of the few manufacturers that separates Core and Player functions on separate computers in their higher end devices. You don't need this. You just need an awesome Roon Core.
The K41 is that. It supports up to three 8 TB SSD cards that are plugged directly in the back without having to open the case. It will support any Roon function you can think of and is incredibly quiet and quite analog sounding. Just run an ethernet cable from it to your T2. The other twist is they have US service and the devices have been regularly upgraded through the years for a few thousand dollars. The last round of upgrades offered new PSUs inside the boxes and new processors. Nothing is ever truly future proof but they have a long history of supporting devices through upgrade. The unit is $10K at retail.
Full disclosure...I am a retailer who focuses on digital and am a long standing dealer for Antipodes. I sold the Nucleus when Roon sold through dealers and don't sell NASs. I have no relationship with Lumin and am a former Innuos dealer which was dropped because it didn't sell for me.
Good luck.
