Personally I've thought of myself as an audiophile for a long while, listening to my old Senn PX100s and B&O A8s.
I was wrong.
After lurking on the forums for a bit I finally went to a store to demo some separate rigs. Went straight to the HD 600s and thought, 'ok, I can hear an improvement but the price really isn't justified' then the salesperson kindly offered me a pair of HD 650s and my mind was BLOWN. I just fell in love with the warm, lush and dreamy quality of the 650s.
I bought them on the spot.
Since then, I've demoed plenty more head phones such as the LCD 2/3s, HD 800s, Grado PS1000, Grado HP2 and whilst some I have considered sonically superior, they bring to mind my initial reaction with the HD 600s.
So I guess the HD 650s will always remain my babies even when I do choose to "upgrade".
Obviously, I've been using my 650s to blow my friends away. My girlfriend is now trying to cut down on the clothes and buy herself some head-fi. (I'd say that's pretty successful)
Although I find the secret to wowing people with your gear is actually with the recording quality. Pick a really well mastered lossless track designed to demo extremely high end hi-fis and the like immediately and they will notice the difference immediately. First impressions are key and if you play Ke$ha of the bat.... even I'd go running for my iBuds.