Which one is better?

Option a seems rather expensive and you'd have a redundant DAC. A Superuniti would be cheaper. Better than a Uniti if you stream from a NAS rather than playing CDs.

(a) sounds a bit of a strange combination (IMO).

When you say "listen to CDs" are you looking at ripping your CDs or do you want to listen to the original media.  Personally I would suggest that ripping will give you as good as playback, but I'm not going to try to convince someone dead set against ripping...

If ripping, then forget the UnitiServe (IMO).  Infact forget the UnitiServe whatever you are doing.  The DACV1 fed into the UnitiQute to me has no purpose either.

Assuming this is a first system ... I would ... buy a UnitiQute or SuperUniti and a pair of speakers.  Add a Innuos Zen as a ripper / NAS / server.  But thats a gut instinct reaction ... only YOU can decide what is better between two options / setups for YOU; and you need to listen to decide.

If you want to play back CDs, then (and I make this suggestion at the risk of being tarred and feathered) add a disc spinner such as Rega Apollo-R or even a Pioneer or other Bluray player.

Agree with what was said above, I would rip the CDs and get a Superuniti for streaming.

I'm with Eloise here - a Superuniti and a Rega Apollo would be my choice. I'd add a Qnap nas for ripped and downloaded music. No redundancy and great sound.