I have posted much on my system and 3rd Party equipment into the BL90s.
The issue comes down to perceived value (price, quality, usefulness etc) and how you wish to connect it?
- Whatever you buy, connect directly to the BL5. Im very cynical that "beovisions" and "wide-body" Beolabs go together well sound-wise.
- Do you want to connect via Analogue (RCA) or Digital (CoAx). There are pros and cons to each.
- What are you listening to? Ripped music on a NAS, Hi-Res Streaming or something else?
- Try and trial equipment at home if you can. The control systems (more often not iOS controlled) vary.
- The BL5 may need the volume cable connecting and possibly a dedicated Beo4 for volume??
Equipment (from my experience)
- BS Core. Currently EoL, full B&O integration but relatively poor in terms of streaming quality. Muffles the sound of the BLs like Beovisions
- Auralic Altair G1. EoL but good bargains now. internal DAC and RCA Output, add a HDD, Killer app and takes Qobuz, amazon, Tidal (Spotify HiFi once released). I have a Altair connected to BL17's. works fine.
- Auralic Aries G1. Top quality. Digital Coax out, Wifi receiving Streamer. Otherwise as the Altair. Again, lots of bargains out there.
Highly recommend whatever you go for (Core/Auralic/Other), that you know the controls, operability's and limitations. Almost anything at the cost of the BS Core or above...will blow the Core out of the water sound-wise with the "wide-body" Beolabs. Loss of integration is the price.