Hi Guy 13,
Your story is amusing to me since it's more or less my experience when I came back to Vietnam after 10 years living abroad. I thought my adventure into the audio world stopped then, until I went to those shops making friends. This hobby is all about to meeting people and trading/upgrading your gears and the community is part of the game. There is a huge headphile community here, if you're willing to look for them.
Speaking of your combo, the Crack/HD650 is a mighty one and is pretty close to the headphone nirvana IMHO. Compare it to a Stax system of course is not a fair fight. I have yet to experience a good Stax system long enough to make out how much it's better than the Crack/HD650 but I think from here, moving up the ladder get you very small improvement for what you have to pay for and is more of a "gain something, lose something" experience. Chance that if you replace your HD650 by something else you'll quickly find out the cons of your new system and will start to look for a new upgrade. This hobby never stops until we find our peace of mind or until our wallet is absolutely destroyed, whichever comes first.
Drop me an PM if you want to make yet another friend here in this noisy, crowded yet charming city.
-PH-