$75 - Grado SR60e (MSRP $79): to me the VERY BEST headphone at this price and one of the best at twice the price... a bit more bass than others in the SR ("Prestige") series; though I have nearly EVERY Grado model (top-line PS1000 arriving this week), I listen to my SR60s as much as any of them to just marvel, with a smile on my face, how something so relatively inexpensive can be so "presence" sounding and comfortable. Many people prefer the next one up, the SR80e, but at MSRP of $99, you'd want to find it used to get it for $75.
$125 - funny price point that falls right between the SR125e (MSRP $150) and the SR80e ($99) - if I were trying to hit $125, I'd go for a used SR225e (MSRP of $199, used price of 2/3 that or $133 or so)
$175 -- again, a price point that straddles MSRP of various models. I'd shoot for a used top-of-the-Prestige-Series SR325e, MRSP of $299 and 2/3 that for like-new used of $199.
$225 -- new SR225e for $200 MSRP.
$275 -- somehow you have to have the SR325e on your list... it is the brightest of the Grados, a caricature of the transparency, presence, and fast treble response that go with the Grado sound. They list for $299.
$325 -- find a used RS2e, MSRP of $495 new, probably could get for 2/3 of that, or $335.
Dang, I LOVE questions like this that allow me to rhapsodize about various Grado models. Wanna hear me recite from memory the construction materials of the cup, grill, and such of each member of the Prestige Series??
A weakness of this is that I did NOT include any of their IEMs (iGi $89, GR8 @ $299, GR$10 @ $399), nor related brands, such as the Alessandro MS1, MS2, or special versions as custom made for head-fi,org, which are the HF1, HF2... I have not actually heard any of these so I would not be giving anything other than opinions of others.