Hi, I'm trying to look around for a desktop amp that can drive my Fostex TH500RP. Back then when I got the headphone, it sounded decent when I paired it with the Hifime (ES9018K2M DAC) > Cayin C5 > Viper4Windows (equalizer software for windows). However after several windows update, the Viper4Windows stopped working and the TH500RP doesn't sound that good right now. It is a very recessed headphone and although my Fostex HP-A4BL dac/amp drives my 650s (300ohms) and T50RP (50ohms) pretty decent, the TH500RP just doesn't pair well. I was looking at the Valhalla 2 OTL amp (since many says it pairs well with the HD650) however I stumble over another thread that says OTL amps are not recommended for orthodynamic phones. Then I come across the Beyerdynamics A20 amp which drives high impedance headphones well but there are not much reviews on it and the TH500RP is only rated at 48ohms. Thus I'm open to suggestions on what headphone amp you think might be able to go well with my TH500RP. I suppose it needs a mid-forward sounding amp. My connection would be Windows 10 (source) > Fostex HP-A4BL (rca out) > *new headphone amp* (rca in) >headphones. That or even another dac/amp within my budget range you think may go well with the TH500 and/or my headphones (in my sig).