To be honest its your car and fit what you want,
I do 40K a year, (Done 170K personally in my 330d) have a race car a road bike and a track bike, therefore quite a few miles and lots of tyres
I truly believe if you ave been running a mid range tyre then the Nankang's will feel pretty ok when new compared to your worn Khumo/Falken, but in real terms they are a mile away from Michelin/Goodyear and Continental.
It also depends on your style of driving, my mum could drive my car for 12 month and not notice the difference between a Conti and a Remold as she barley goes over 60mph, works in the centre of Birmingham and mainly in traffic.
I however live in the country do massive mileage inc lots of motorway, and its said i on occasion drive enthusiastically, this is when you see the differences between the tyres, especially in wet weather and standing water.
My experience of Nankang (yes i did try them) was after a few thousand miles the grip dropped off and never ever had the confidence in them, the road noise was a lot higher as well, i ditched them with 5.8mm left (sold them on ebay actually), i think the best of the midrange were Falken's even though i didn't get massive mileage out of them. (just under 10K on rears)
Even though i have tried them and have an open mind, i have gone back to Conti or Goodyears (Goodyears seem to last 2-3K more than Conti, also Contis at just above legal limit arent quite as Goodyears but for out and out grip down to 2mm there excellent)
We have also tried lots of road tyres on wet track days in a 400bhp FWD car with a gripper diff when its to wet for semi slicks, and the rainsports are excellent
So as said, its up to you what you fit and if your happy then great its your car and its you opinion, we all look for different things.
Road Car Conti or Goodyear (Michelin are excellent but more expensive) (330d remapped, decat, performance system, EGR Delete)
Track Car - Dunlop DGZ03 (semi Slick) (400bhp FWD, 32psi boost and 350 ft lb )
Track Car Wet road tyres - Rainsports or Full wets (not road legal)
Road Bike - Michelin Power pilot 3 (or road pilot3) (110bhp)
Track Bike Pirelli Super Corsa Diablo SC1.s (soft Compund) (125 bhp)
Just remember opinions are like arseholes, (we all have one lol)