Hi, I recently purchased a mantel surround after doing extensive research both locally and on the web. I found a great deal on Ebay.com from the Appalachian Mantel Company. They post some of their mantels for auction there and it is possible to get a deal. You can also buy direct on their website. They custom size the unit to suit you and the ordering is very easy and the mantel was at my door in less than 3 weeks. Install was a breeze. I have no affiliation, I am just a happy customer.
Their website: http://www.netease.net/amc/ourmantels.htm
One of their current auctions on ebay: http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=465058894