I've owned both headphones, and still have a set of Portapros that have been on loan to various friends for over a year. I would say they have similar low bass quantity, maybe the 650 edging, but the Portapro has more upper bass and mid bass.
To the OP - mate, a better headphone does not mean one with more bass.
By your logic, if the 650 should have more bass than the Portapro because it is more expensive, then the HD800 should be able to kill you with its bass while the SR-009 would leave cities in rubble?
You will find entry level, mid-fi, hifi a TOTL headphones that have lean bass, neutral bass, heavy bass - something for every taste.
