I agree with those who posted you should buy the best you can afford. I do shop online primarily since the LQS around here are very expensive. I can usually find excellent quality quilting fabric for much less online. One of my favorite sites is www.quiltshops.com. On this site, you can find over 200 quilt shops listed. If you are searching for a particular fabric and can't find it, you can usually find it here.
My second favorite is www.stitch-n-frame.net. They have sales every Thursday which are posted on Wed. night through Friday morning.
My third favorite is Craft Town in Salem, IN. Craft Town's clearance prices are wonderful; especially around December. I bought 3 different sets of Moda Charm Packs for around $5 apiece in December.
The fourth would be www.whittles.com; located in Bowling Green, KY, about 55 miles from me. If you are close enough to go to the shop, the cost per yard is about $1 a yard less.
Number five: www.quiltsrjewels.com; located about 15 miles from me. Great prices.
Good Luck!!