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

I am a regular on smile.amazon.com (where they donate .5% of my purchase amounts to my favorite charity), have the Amazon credit card (giving me 5% cash back) and have an Amazon Prime membership, enjoying 2 day shipping and Amazon Streaming to my TV.

Besides all that, I find the reviews on Amazon really helpful, especially as I'm learning more about classical music.

"The brunt of the question is pretty much covered in the title, but just curious where most people are buying any physical medium of music (vinyl, cassette, 8-track, etc.) online."

Where's the recommendations for cassette or 8-track? Got to say I was a little amused that they were included in the list. Guess they can still be found on ebay or craigslist.

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...