What is your go-to online place to buy physical medium of music? And why?

Thanks everybody! Personally, the only thing I'd used for online purchases is Amazon. And it sounds like a lot of people corroborate that choice. Some of the other lesser-known (to me) options look really good as well so I'll definitely check those out. The interface of Discogs I like pretty well but, personally, the Goldmine Grading thing just seems kind of non-sensical to me.

@tls49 haha. I personally don't listen to cassettes or 8-tracks anymore but, surprisingly, cassettes are actually making a significant comeback - similar to how vinyl has had a huge renaissance in the past 10 years.

A couple of interesting articles about the resurgence of cassettes:
- http://www.forbes.com/sites/jasonevangelho/2016/03/24/forget-vinyl-lets-talk-about-the-cassette-come...
- http://www.cbc.ca/news/canada/toronto/programs/metromorning/cassette-tapes-comeback-1.3490619

I’d say 90-95% of my music comes from these 5 suppliers.
Amazon
CD Universe
CD Japan
Elusive Disc
Presto Classical

@jeffdill2 I didn't see any mention on genre. Luckily we have great local shops where I live headlined by the Attic. If I do go online for records I like:

for electronic, dj, world, hip-hop, afrobeat, reissues: Juno, underground hip hop, fat beats and turntable lab

for used/new jazz and world: dusty groove (great store in Chicago)

for indie/Rock: Insound, amoeba

For good selection if you don't mind imports: import CDs (plenty of vinyl)

for a general catch all: amazon

i travel for work and make it a point to carve out time to dig in other cities...if you do as well build a rapport with the shop owners with your preferences or wish list and keep in touch with them. 

Also, check with your local stores and ask if they discount for pre-orders. A place here will give 10% off if you "place an order" with them. 

Good luck...

@jeffdill2 I forgot band camp website too..