It depends what your preferred sound signature is and library. B2:Dusk is tuned to be neutral with a bit of bass boost. The Teas mk 2 have more mid-bass / warmer sound and a "darker" treble, which basically means non-fatiguing but still resolving. The mk 2 is already an improvement over the OG Tea, which many have said was too warm and too dark. The mk2 is slightly more analytical. Still not as resolving as B2 and some would absolutely hate that. Both versions of the Teas have a special 3D, holographic presentation. Moondrops in general are...neutral and tbh a bit boring to my ears. I also find Moondrops very uncomfortable for my ear canals due to thick nozzle.

I will note that I used to go by Crin's ranking list as a way of dipping my toes in the IEM world. However, in time, I've realized that his preferences are very different from my preferences. I prefer warmer sound signatures and have moved away from all of Crin's recommendations. Top tier IEMs in my book rank low on his list, but thats okay. There is no right answer since everyone is different. Its just a matter of getting to know what you like and not like.

So if it were up to me - yes, the Tea mk2 at $279 is a great buy but YMMV.

edit: regarding your quote about "waiting for somthing better"...is basically chasing a unicorn in the IEM world. Things move very fast and there is literally the next best thing in a week.

I haven't had the XS since they were first released late last year but from memory, you will definitely get more "slam" and bass extension than HD650. The mids on XS are scooped and it would an adjustment coming from HD650. Not necessarily a bad thing...just different. Hifiman cans tend to have a dip in the 2K region but it was quite noticeable on the XS. Nothing a bit of EQ can't fix. The mids are definitely better on HD650s. Treble is as you described...much more forward and detail retrieval is much better on XS. The one thing I will say is that the soundstage is much wider and open on the egg-shaped Hifiman. That will be something you will definitely notice vs. HD650. At the end of the day, yes, they are different enough to serve as a good compliment to your 650s. I just don't think the XS compared to the HE-500 so I ended up selling them.

I will say this though...I did the Custom Cans mod on the HD650 and it made some pretty significant improvements to the stock sound. So much so that I've sold the XS but still have the HD650 so it says something about how much of a staple the 650s are in any collection.

Dunu Falcons or the limited edition Vernus are pretty good DDs. They leak sound like crazy though.

Unpopular opinion but the Penon Vortex is a very good DD IEM.