It's difficult to know if this is exactly what you're looking for, specially because I don't have much experience with neutral sound signatures, but here is my opinion.
The Meelec CX-21 offers a neutral sound signature (well, neutral to me) at a very decent price.
The problem is what do you consider to be "neutral", because you mention "I really want flat sound that requires no eqing of any sort".
Not needing eq doesn't mean "flat". In fact, flat response phones would sound a bit weird. So, it's a matter of sound preference here. I don't use equalization with any phone I have, and all of them have very different sound signatures.
The CX-21 are neutral, but I also consider "neutral" most of the cheap balanced armatures out there, like the SoundMAGIC PL50 or the Meelec A151, even though the basses of the first may be sound "weak" without eq. IMHO, the Re-0 would also fill the bill, even though the basses also may sound "weak".
Difficult question, so.