Congratulations. Nice speakers. NAD is a brand many people start with. Good start.
If you have just completed assembling this, you may not want to swap boxes yet. You want to become very familiar with the sound but aid with cable choices like you said.
So, it makes sense to warm it up. You want to look at Cardas cables and interconnects. They are specifically designed to be warmest at their most budget oriented levels and to become more neutral as one moves up in their lines. This is what is typically needed as you move to higher level components.
Early on in my audiophile career (~40 years ago) my system was too bright and Cardas Golden Reference did exactly that. These were high end warm cables they used to make. Anyway, years later I made a big upgrade and I immediately pulled them off and moved to more neutral wire. You are thinking correctly. If you can get it sounding warmer, then you can really work to position it correctly and tweak it, and fix up the room. And it becomes your reference for a few years until you choose to upgrade.
When you choose to upgrade. Most of us have individual boxes for streamer, DAC, preamp, and amp. The more boxes, in general the better things sound. Each is optimized and isolated from othe functions. If that simply doesn’t work then a streamer / DAC and an integrated amp. Can work.
Also, setup and room treatments can make huge differences. There is a place to show photos your system and venue. We can be really helpful if we can see your system. They need not be show photos. You can see my system under my UserIDs.
