By far the best place for cables is Monoprice
scroll down to the bottom of the page and you shall find a 10ft cable for $7.10, 6ft for $5.84, scroll up a little higher to find 25ft for only $19.40.
Basically the stores make a high margin on the cables they sell, so buy a cable for the cost of the cable not the cost of the name.
I have purchased from monoprice several times and everything is higher quality than in most stores and works 100%.
Once you shop for cables there once you will never buy another one in a store again.
HDMI-DVI adapter at radioshack is $29.99, at monoprice it is $4.97
They are amazing and if you don't believe me check out the AVS Forums
? where video and audio experts give them high praise.