Best all-rounder for ~$300 new or used?

[AndroidVageta]

  go ciem bro.. or you can try dita..

Eh I couldn't quite agree with that. CIEM's are definitely where the best is...but not in my price range. I'd bet money that the likes of the EX1000 or DN-2000 would be a lot better then ANY CIEM in the ~$300 price range. 
 
As far as Dita goes...I doubt they're far superior to the likes of the EX1000...if they are (reviews aren't bad at all) then I'm sure I'll give them a shot at some point!

 

[joey99]

   
Probably not better than the Altone based on reviews, and definitely not better than the UE900. I had one for a few months and it was very fun but only worth about the $75-100 asking price.
 
AndroidVegeta, I feel the DN-2000 is also a good place to start, but haven't gotten one yet. I had the EX600 for a few months and it's said to be similar to the EX1000 just not as refined, and I thought the EX600 was world class. Also a good contender.

For me even my H3 betters the UE900 by a mile .... so I think it's so very personal preference and only you will know what you like when you hear it.

 

[faithguy19]

I would probably agree with Joey.  A lot of the time it is simply finding something that works for you.  I hope you are able to find it.

 

[Tympan]

I have the FX850. Excellent sounding earphones but not a good candidate for an all rounder type of iem. It is huge, kinda awkward to wear, and the sound is pretty BIG. IMHO, it sounds phenomenal IF in the right mood. If not, it can be totally overwhelming to me as well and so not in a sense that it sounds bad but in the sense it has so much body to the sound, it's a massive wall of sound in you face. EDM repetitive bass drum may leave permanent imprints on the brain, feels like it to me at times anyways....
So, instead, I would recommend the Re-600 as an excellent and affordable (under $199) all rounder.
These earphones sound quite different from RE400 imo. More bass, sweeter mids, better depth and soundstage, more alive and musical overall...Plus the slightly rolled off treble does not suffer from any sibilance. 
Finally, the Re600 are very discreet and the most comfortable iem I have ever owned (along with the Re400)... worth considering them in your short list

 

[AndroidVageta]

 

Thanks! Yeah, I owned the RE-400's and thought they were very...muddled? Nothing really stood out and the treble was way too subtle for me.

 

[Tympan]

Well, not sure you would like the Re600 then. Best thing is to audition them before buying (although some retailers do accept returns...)
Best of luck with your search!

 

[Valkayrie2]

If you're a basshead, some reviews of the RHA T10i seems to be where you would prefer. Don't have them myself so can't tell you anything about them but there are some very detailed reviews here on them.