No experience with Naim power upgrades as my amp is a Nait XS2 so I think I’d probably upgrade to a SN3 before thinking about power upgrades. I also have a ND5 XS2 streamer that I’m very happy with and it works very well with the Nait.
An ND5xs2 will give access to Qobuz and Tidal natively via the Naim app and fit the level of your amps. Any CDs you have will need ripping, with a couple of thousand I found the Uniti Core convenient but the job can be done on a computer if you have more patience or fewer CDs. The Innuos rippers are an alternative that also stream so all you need is a DAC, a used Naim DAC would fit right in but you dodn’t get to use the Naim app that way. See the tail end of the end of my tether thread from around post 950
you’ll need some patience for that too.
If you have greater ambition than xs level than skip to the NDX2, unless the innuos/DAC route appeals.
If vinyl plays a big part in your listening, and it’s primary in mine, than upgrading the turntable comes into play and maybe before considering the streaming options. The recent Regas are very good but there are plenty of options to explore if you feel more adventurous, the Well tempered simplex and Versalex have impressed with their musicality with the right cartridge.
Up grading source first is the traditional flat earth strategy and avoids playing catch up where a speaker upgrade reveals faults in the system above which you then spend time and money to address while they gnaw at you. This assumes that your current speakers were well chosen in the first place but your room and tastes will be a factor so only you can decide. Home demos are very valuable and never more so when choosing speakers.
Decide if I was happy with CDs or wanted a streamer instead.
Decide if I was happy with 5 series equipment or wanted something better
If happy with 5 series get either a CD5XS or a ND5XS2, and a Flatcap 2XS
If not happy with 5 series, get a CDX2 or NDX2, and swap the 152/155 for a Supernait 3
Get a Rega Planar 6 or 8 - this could be done at any point
Other brands of equipment are of course available but this sticks with Naim to keep matters simple, other than the TT suggestions of course. It also assumes that the GB1 bookshelf is in fact the DB1, which hopefully are on good stands.