I highly recommend Marshall Street. I've been using them for years. Their website is a little slow about loading additional products on any given page. The photo of the disc on the scale with the actual weight of the disc and the way they number them allows one to get the exact disc you are looking at online, as opposed to someone just grabbing a random disc out of a box of many.
I received a gift certificate from my daughter for Christmas from Discs Unlimited out of Kansas. The discs were overpriced, so I ordered some accessories instead. They shipped the incorrect item, when I let them know I received the wrong item, I received a PDF of a return label only. No apology, no explanation of how to proceed. After a week I returned the incorrect item, thinking they were waiting for that to then ship the correct item. After another week I got an email saying my daughter had sent me another gift certificate. (she did not). Still with no explanation from any humans about how to proceed. I sent them another email and requested they refund the unused balance to her card. At this point I finally heard from a human, and they did refund the balance. Their lack of communication made this a very bad experience, and I am unlikely to ever use them again.