One of my favorite nurseries is Lincoln Oakes, which is run by Soil and Water Department Districts in North Dakota. I've used Lincoln Oakes for the last seven years and it has prices comparable to the MDC, and sells seedlings in various sizes/year groups. I've purchased Lilacs for the yard, Golden Current, Serviceberry, Arrowwood, Wild Plum and others from Lincoln Oakes, and have always been satisfied. It's a northern nursery so its seedlings are acclimated to MN & WI, but also grow here in MO.
http://www.lincolnoakes.com/stock/pc/home.asp
http://www.lincolnoakes.com/stock/pc/home.asp