Spk cable with deep,lush,spacious sound....

I agree with Jkaway(John) that if you try the Alpha Core Goertz MI-2 copper ribbon there is excellent chance you will get exactly what you are looking for. I formerly used MI-3 which is same sound as MI-2, for its power amp rating, according to the factory rep I spoke with. Although not the "best" cable at its price for detail or three-dimensionality, it is close, being excellent overall, musical, and a bargain when bought used on Audiogon.

Stealth Ultimate Ribbon should work good for your requirement. Nice warm top, full mids with good chewy bottom. The AZs are punchy but less musical than the stealth. Cardas seems to sag. XLO is a bit on the grainy side. Overall, NBS Master probably the best. Punchy, musical, but not as warm as Stealth.
I've tried all the above in different tube systems. These are just my opinion.

In the past, I felt Analysis Plus Oval 9 accomplished most of these things for me, and more recently the Acoustic Zen biwired Hologram II, and Audience AU 24 were standouts.

I agree with S23chang on the Stealth UR. Very smooth cables with a good bottom end. I had them for about a year and only sold them because I bought new speakers.
They work very well with "leaner" systems.

My take on speaker cables based on my experienced alone.

I've been to the Acoustic Zen route (Satori first then Hologram MKII's for several months) as well as Analysis Plus (Oval 9 double run), Purist Audio Design (Museaus, and Colossus for a brief moment), Synergistic Research (Designer series), Nordost (Blue Heaven Rev. 2 bi-wire), MIT (330 and 750 if I remember correctly). The longest time that stayed on my system (2-ch) is the Hologram MKII. I still have the Satori though for HT.

From extensive reading, I was very intrigued of what I've found. Most of the highly respected DIY'ers (Chris Brady of the Teres Audio fame for example) does not use any of the cables that I mentioned above. In fact, a great majority of them uses the ff:

Teflon encapsulated, evenly spaced, pure Silver Wire (at least 99.99%), bare wire termination. For bi-wire requirements, 16 ga. for the woofers and 18 ga. for the top (this ratio is very important).

Tried it and the result for me supports my accumulated experienced in selling the majority of speaker cables that I tried above. Best of all, bi-wire config for 6-8 feet pair only cost approx. $6.95 per foot.

Maybe you will be interested to try it. Again, it works for me but cannot confirm that it will work for you.

Just another option you might find interesting....