I listened through my SR-80s without an amp for several months and was VERY happy. I plugged them right into my archaic Sony portable and was pleased. I do have a hand-made DIY amp and indeed, it does sound better (more filled out) than with just the headphone amp on the portable, but if that amp wasn't around, I'd still be as happy as a pig in slop.
I know that $80 may be a challenge, but I'd be writing a petition in favor of these headphones, walking door-to-door and giving my neighbors my pitch, and ask for a couple bucks. "My ears thank you, kind sir. You're doing a service to the people of British Columbia. Vive head-fi!"