I recently purchased the IE300 as a "test" for a possible future upgrade for the 600 or even the 900, despite having the idea that the 600 could be the "smarter" choice if considering bang for the buck.
I must admit that I was pleasantly surprised by the SQ considering the price. IMO, it performs better that the price suggests.
I was ready to upgrade the tips, but the stock middle one that came already mounted were just perfect! I had the Campfire Holocene before and with that type of IEM it was always a struggle regarding which tip to choose as to fit and stay put in my ears.
The Sennheiser are my first deeper in ear format and in all honesty, I'm much more into IEMs now! (Still prefer Headphones nevertheless
).
What was a dreadful no-go, is the cable. Are you kidding Sennheiser?!!! And thinking that it also comes with the much expensier siblings is absolutely unacceptable in every sense. My left IEM piece wouldn't even make a good contact with the wire, had to fiddle with it constantly, the microphonic and memory cable is just a plain nightmare to "work" with. I was almost returning it, which desolated me because I was loving the Sennheiser for everything else.
So I ordered an inexpensive Tripowin cable (I read in the IE600 thread that these were direct fits without having to fiddle with the connections) and it worked without having to change anything. In my case I ordered the Linsoul Tripowin Zonie 16 Core one but there are tons out there in Amazon.
That changed the all experience to the next level! So happy now! For the current price (usually heavy discounts are in place) I believe this little IEM is a no brainer! But consider upgrading the cable as soon as possible and wait for it to arrive to order tips (in case you don't already have third party ones) because the stock ones may just fit you. I was even surprised because not even the large ones would seal my ears with other IEM´s but with the Sennheiser the medium one is just a lovely fit. I guess it is related to how this type of construction goes deeper into the ear canal and therefore interacts with the tip.
Cheers!