Stax cables for the best. Their headphone cables are very flexible and durable.
For the worst? Hifiman cables. Cable material feels nasty, and right-angled plug is questionable for desktop use.
For IEMs the Sony EX800ST stock cable was the worst. Didn't like memory wire for the ears, cable felt too thin and flimsy, and 1.6 meters is too long for an IEM cable.
I think it can be worth it depending on the use case. DAPs are a no-go if you're only streaming music. Also harder to recommend DAPs these days though vs 5-10 years ago cause mid-range DAPs have gotten more expensive and there's limited options for entry level. The main draws for me are the dedicated buttons and being separated from my phone (no dongle = less USB port wear while in the pocket).
Right now I'm using a Sony A306 as my daily driver with IEMs, has a great battery life so it won't be racking up too many charge cycles like my other DAPs. I still use a Fiio X5iii (dual SD slots) at home for headphones so the low output power of the A306 doesn't bother me.
I have an old Shanling M2S that I used to daily cause it could also act as a bluetooth DAC/amp for my phone but I sidelined it in favour of the A306. Has the average DAP batt life of around 10 hours so it racked up charge cycles really quickly.
Stax L700.
The Focal Clear closed the doors to dynamic and planar upgrades, but it was the L700 that killed the upgraditis
Focal Clear OG.
If the L700 is immersive, then the Clear is engaging. The forward upper mids and punchy bass always makes me nod my head to the music.