Let me inform you. I was in the headphone store auditioning the Grado 125i, 225i and 325i yesterday, and comparing them closely with the HFI-580, i spent one and a half hours doing it.
The HFI-580 does not, i repeat, does not have strikingly obvious forward mids, maybe just a tiny bit, but not very prevalent as a defining sonic characteristic, plus they have an overall darkish tone to them for some reason, despite sounding balanced all over, however, they definitely have recessed upper-mids, which probably contributes to the overall darkish tone of the 580, but i will say that even though initially they sound fine and dandy and clear to some extent, eventually you will crave to have the upper mids back in the picture, it's inevitable.
But i can happily tell you that the Grado 125i is around the same price and has overall attributes very close to the 580 and with a sound-signature which is very similar but without the recessed upper-mids, also the Grado 125i is not so heavy in the bass department, but the bass still sounds more than adequate, not underdone like the Shure 840, and they have a great overall sound.
Believe me, you cannot go wrong with the Grado 125i, especially at that price. The 225i is a bit more transparent than the 125i from the mids to the highs and this attribute is apparent in the 225i compared to the 125i, so the overall sound of the 225i is a bit more clarity and definition in the highs, maybe a tad too much actually, so the 225i does not make the 125i sound inferior to any significant extent.
If i could only buy one headphone and to a budget, the Grado 125i would be it. And as a bonus, with the Grado headphones you can use two types of ear-cushion, one which covers them 'flat' acrooss the face of the driver, and one that sits around the outside rim of the ear-phone cup and leaves the driver open (but it still has fine mesh over it of course), and as a result (Just like the headphone salesman said to me) you essentially get two different headphones for the price of one, and i can confirm that each ear-cushion does indeed allow the driver to display a different overall tone, both of which sound pleasing to me, but surely you will probably end-up liking one more than the other, so anyhow you can't go wrong.
You are in an enviable position from my point of view. I've already wasted $1500 buying headphones which i eventually didn't like, an so it's taken me that much money to arrive at a good headphone, which i am for the most part very happy with. But it sounds like you are just starting-out so to speak, and thus good advice like this from me will save you money and time and energy. Cheers.