Alliance Entertainment owns DirectToU, which is the company doing business as Deep Discount, Import CDs, and Collectors Choice. I don't believe Movie Mars is part of that family, but I could be wrong.
I've bought a lot from decluttr (and whatever they used to be called) over the years, and my experience is that the quality of discs has gotten a lot worse within the last 12 months or so. I think I am probably done buying from them for a while.
Edit: DirectToU also operates the Popmarket site.