My tv just arrive today sent by GDex. Pay june 24th. Trusted

The KS series from 2016 are indeed spectacular TVs , it is just pathetic Samsung keep removing the features from current line up & put them on separate models to sell for higher price  .
NU8500 is basically the curved version of NU8000 .

I don't think they are comparable with the KS series  because NU8500 / NU8000 isn't a Quantum Dots TV.
If we have to compare , the KS7500 should go head to head with Q7FN , in which the Q7FN is an upgrade in almost everything especially the brightness .

55' of NU8000 is retailing @ RM4199, 65 inches @ RM6299 , that is still quite a bit cheaper than the now 2 years old KS7500 .
The KS series are definitely a looker especially when it comes to HDR performance. They can reach very high peak brightness in small windows , which ensure those shiny small highlights to glitter in dark HDR scenes. While the NU8000 can't reach the same peak brightness but it is overall , a brighter TV  .

The one small problem with the KS series is , they can't sustain the same level of brightness they used to display specular highlights . It is mostly a glimpse into the spark and the brightness quickly fall flat on screen . NU8000 and newer QLEDs can maintain the same brightness level for a long time. This is especially noticeable in prolong HDR scenes with bright objects like the torches , the sun ,  the moon , the stars etc etc .
I've mentioned before Samsung is dropping the ball for their entry~mid range models every year . KS series is a lot more impressive than the 2017's MU series . The 2018 's entry level models of the NU series are disappointing as well.

A while ago they had installment with interest charges up to 12% .
But I am unsure now , best if you give them a call to confirm.
Yea IPS TVs usually have terrible black levels in dark / dimmer room .

So just put on some lights , the ambient lights mask the grayish black really well  , that's why its hard to tell the TV aparts in those showroom and shop displays .
Judging from your usage , the XF70 (x7000f) will serve you well.
Sorry to hear about that , when you got a defected or a broken TV it is frustrating . Makes you question your purchase decision.

But let's look at the brighter side , at least you are buying from the major brands & they are willing to repair / replace your TV normally.

I probably have recommended this particular model to hundreds of people , so far only a few of them are unsatisfied ( mostly nothing to do with malfunctioning units )
When you buy from the bigger brands , it doesn't mean all their units will be perfect.  It just means they usually have better QC and the odds of defects are relatively lower .

How much though net of cash back? And what's a power stick if you don't mind me asking