I still listen to my HARX700s (had for many years)...recently installed some HM5 pleather pads (not the angled pads...they weren't on sale at the time...). They still sound pretty damn good. I am using an Aune T1 and FiiO E9 atm. Both drive it quite nicely with plenty of volume. I use Equalizer APO + Peace UI for an EQ. The pads are more comfy, and add more space between your ears and drivers. This does make the mids and hi's more distant, but still in your face and the bass is still plenty powerful and a little more prominent imho. These things are built like tanks, I have a brand new spare pair at the ready. Took about 5 minutes of stretching and cussing to get each pad on, but it was done with success and was worth it!
I also have some Denon D2000's, JVC HADX3's and some boxed up HE-400's I am supposed to be selling atm.
The D2K's are parked until I finish repairing the hinges, but have a more laid back sound with deeper, but less punchy bass compared to the 700. The mids and treble have more details.These can be bass monsters for sure. Mine are bone stock too. They've been fun, and they do sound good...they don't isolate all that well and are a semi-open can not a fully closed can, they are vented and the cups are thin and let a lot of noise in and out.
The HADX3's are a brighter and more detailed headphone that also can have 3/4 of the lower bass that D2K's have. The hinges squeak sometimes which is annoying, the isolation is pretty good and the velour pads are super comfy. These require quite a bit of EQ tuning to get bass out of them though, and a more powerful amp helps. These have treated me quite well overall, but have considered selling them because I'm not as much of a treble fan. Don't be mistaken though, these can pull out a lot of deep rumbling bass.
The HE-400's are in a different league. Being open back, some of why they are is because of design. It also sucks because I have a lot of ambient/background noise so I have to crank my tunes more...which bothers others in the house..sigh. First world problems. Anyways, they are amazing, and if you have a good power output (I've used my Aune T1, FiiO E9 and Denon AVR-1613 all with great success), and don't mind EQ-ing the bass up, the mids up a little around 1k and the treble down a notch or two, they will blow you away. Or they did me. Took me over a year to accept that the velour pads are more comfy and do sound better, but its true. Many recommend getting the HifiMan Focus pads for these as well, for comfort. But the HE-400S are out now, which have the more comfy headband, might be worth a look.
I have read good things about the A900X, and have been tempted to find something that's a step up from the DX3's and RX700s in terms of my AIO can on a budget. I keep going back to the 700's because even with the HM5 pads and increased space between driver and ear, they are still more in your face and fun to listen to, and the punch bass is still pretty damn good for such a cheap can.
I have some Sony XB-500's, but I don't listen to them ever, and the second pair is what the missus and kids use.
If you can raise your budget, you might look at the Beyer DT990 semi-open headphones, more detailed, better in all areas, and supposed to have amazing bass. I'm tempted to check these out barring some more research as well. I've never tried Beyer cans...but have heard many good and some bad things about them. Some might recommend the DT150 or 250 as well, depending on how much more detail you want. On a budget there is always the give-take.
Another can I was researching is the SoundMagic HP-150. Supposed to be great bass, isolation, decent fit and build, better mids and hi's with good detail as well, some have replaced more expensive cans with these, though they are a few bucks over your budget. I do have concerns with the hinge breaking as they are mostly plastic and some have experienced this...but who knows.
I guess it depends on if you want closed or open as well.
