You may want to checkout Restockit.com for cake boxes. I just placed an order for some boxes.
My order is below. This week they have free shipping on orders over $75. Normally the rate is $8.95.
They also have uncoated cake circles in 10, 12 and 14 inch.

Order (each case of 100)

Smyrna Container Bakery Boxes, 10w x 10d x 5 1/2h, White
$30.74
  
Smyrna Container Bakery Boxes, 14 1/2w x 10 1/2d x 5h, White
$48.74

Smyrna Container Pizza Boxes, 14w x 14d x 1 1/2h, White
$25.54

I also picked up a case of black bases and clear plastic domes from Sam's Club last week. They will hold 10 & 11 inch cakes (12 inch cake board). They are the same ones they use for their round cakes. $39 for 50.

Have you tried their cake bases? i wonder if they are single wall or double wall thickness. It doesn't say. Ive ordered their boxes before and they come quickly as well. very good price. Let me know when you get your cake boards.

I didn't order any of the boards. Now I'm wishing I had. I'd really like some grease proof ones, but I haven't been able to find any with low shipping charges. I was excited with webrestarauntstore until I saw the shipping cost.