The HD600 series are fully open so if you want low bass they won't be the best option. The HD560S has more dampening so has deeper subbass. The Clear has similar subbass extension to the HD560S but cleaner, it's an overall more dynamic sounding headphone, a bit aggressive. Best is subjective. The Nighthawk have good bass clarity but their hump is much different to the TH900 it has a more broad hump that bleeds well into the mids so no matter what, you'll always have this sense of warmth, or echo effect. Nighthawk do best for pop, some rap, R&B that benefit form a little extra something down low. TH900 are great for this too but you may find yourself getting fatigued quicker. Consider the EMU-Teak, they have some potent bass, not quite TH900 potent but pretty good.
Planars whether people like it or not, have much more muted dynamic impact, this comes across more obvious in music that has a lot of bass or general upbeat and poppy music. The pistonic motion of dynamic drivers just handles this better. 99% of Planars also have completely sealed front volume so you don't get hardly any mid bass impact so songs that have decay and heft in the bass will not sound their best on planar magnetic headphones. Most Hifiman headphones are the exception here but as measurements suggest, they have more rolled off low bass or heft and sustain in the low bass compared to say Audeze headphones but have more mid bass presence but again being planar, they still don't have the same sense of impact as dynamic drivers. Even the HD600 have more dynamic impact than any planar.
As I mentioned, bear in mind if you do go Nighthawk, no matter what they'll always be a heavy colouration and lack of distinction but if you don't mind this and see it as some funky quirk, you're most likely going to have a good time as they are pretty fun. 9/10 though I would prob push someone to go for a typical biocellulose tuning like the Teak, old Denon series, THX00, TH900, TH600 etc.