another name that hasn't been mentioned too much but could be in the frame for pick 20 is Ben Newton. He's had a few issues with injury this year hence him flying under the radar but he appears to have all the tools to be a top class midfielder
http://www.afl.com.au/news/newsarticle/tabid/208/newsid/102355/default.aspx
http://www.afl.com.au/news/newsarticle/tabid/208/newsid/102355/default.aspx