it's hard to find stuff in Vancouver....here's a boatload:
Long & McQuade: Senn HD280; AKG Studio series, K 301; Audio Technica pro series.
Tom Lee [preferably Granville and Helmcken Street]: Sony 750x; AKG pro series; Senn HD 280; bunch of DJ phones [ie. Technics, Stanton]
Hi-Fi Centre [Seymour St, near A&B sound]: Grados; Senn HD 600.
Signature Audio [Cambie and West 14th]: Grado SR 60, 80;
A&B Sound: Koss PortaPro, SportaPro; Senn HD 590, PMX 60.
Radioshack: Senn MX400;
Commercial Electronics [Burrard and Burnaby Street]: AKG K301, K 401;almost all beyerdynamics [DT 231 for $150]; Ultrasone HFI650, HFI6000; Senn HD 25-1, HD 570, HD 590, HD 600.
as for prices, the 7506's cost about C$200.....HD 280s cost about C$160-180...and the Grado SR60's cost about C$135-140, i think...
as for other phones...the AKG K271S is about C$300..the Senn HD 590 is about $300 as well, while the the HD 600 is about C$600...and Grado SR80's are about C$170-200
..there don't seem to be any places that sell cheap senn's like the PX200 and the HD 497...wonder where those are...hopefully my list is incomplete..
so that's all I found..hope this helps....