I like to buy in the same fabric grouping, too, but sometimes that's not possible. This doesn't answer your question about matching but I would like to tell you of a great online only fabric shop-
www.fortworthfabricstudio.com. Jodie is the owner/operator and ships the same day if the order is received by 3 p.m. She is very helpful and runs specials each week on Friday as well. I've used the site for several years now and have never been disappointed. I also use Connecting Threads and am pleased.