In reality you can't name even a single pair of hi-fi headphones under $900. Between 300-900 there are some good mid-fi headphones, such as the HE-400i, Nighthawk, and TH600, etc, but these are mid-fi, not hi-fi. BTW, in my opinion the HD6x0 headphones do not fit the category of "good" mid-fi, let alone hi-fi.
Also, there isn't an explosion of hi-fi brands. That segment consists almost entirely of Audeze and HiFiMAN due to rise of the modern planar magnetic, who have left the major manufacturers in the dust in the high end. The ultra high end you have Abyss (planar) and Stax (electrostat). Dynamics are being left behind. The one and only hi-fi product Senn makes (HD800) is pretty bad unless mated with high end equipment and modded -- oh, and it costs $1,000 (old version). There's a number of boutique manufacturers like Mr. Speakers, ALO, etc that puts out hi-fi products, but they are all well over $1,000.
There area huge number of variables -- that boils down to the quality of your equipment in the playback chain, including your headphones. For example, I have a playback chain that is worth around $4,000 not counting headphones. I plugged my $60 Superlux HD668B into it....and it sounded so bad I couldn't bear to listen to for more than a minute. Likewise, plugging my $1,300 TH900 into a $120 Chinese custom build amp from eBay (selected for it's impedance to play well with the TH900) -- sounds like trash compared to my reference system.