It may very well be the DFR can't properly drive the A5-PRO's. I listen with the DFR volume @ 25% and Foobar level ~ @ -14dB) and my SHP9500 does have a little more bass detail, impact, and volume than the A5-PRO's, while the TH-X00 PH has NOTICEABLY more impact and extension, not even same ballpark...the A5's have about 50 hours on them while the SHP9500 and TH-X00 PH each have several hundreds.
Absolutely no headphone has been as comfortable as the modded SHP9500 though, it outdoes the AKG K-7XX (just) in melt on your head and dissapear comfort, and adding the leather headstrap strap is the biggest reason for it. The Shure 1840 pads also brought up comfort level too, but the sound quality increase is the main reason to put them on over the stock pads. You get more lowend, both in impact and extenson, along with more detail and clarity throughout the entire frequency range. Main reason I have the SHP9500 is they are my gaming headset, and they excell at it. They are also great for symphonic and vocals, not bad at electronic either, though they are not close to TH-X00 PH in that category..
I do have an amp that can adequately power the A5-PRO's (4.5W capable output Meier Corda JAZZ-ff), just don't use it much for music because when paired with the DFR the sound isn't as good as it is directly out of the DFR. There is more low end impact, but everthing else is slightly worse, pretty sure it has to do with the amp section of the DFR being fed into another amp. Looking to get a stand alone DAC to pair with it because the JAZZ-ff sounds stellar from the DAC output of my SACD player.
Really want to like the A5-PRO, but I just can't physically stand to wear the phones for more than a few songs at the moment...can't take those on ear pads and headband pressure point on top of head. Until I can get comfort level acceptable they won't be having much listening time at all.