The stats below are from 2005/2006 season to present date and all at Championship level for various teams.

Note the goals per season average is worked out by multiplying 46 matches by 90 minutes and then dividing it by the minutes per goal ratio.

Patrick Agyemang
Matches Started: 68
Substitute Appearances: 64
Minutes Played: 6975
Goals: 28
Assists: 8
Minutes per Goal: 249
Average Goals per Season: 16

Rowan Vine
Matches Started: 91
Substitute Appearances: 21
Minutes Played: 8005
Goals: 30
Assists: 11
Minutes per Goal: 267
Average Goals per Season: 15

Heidar Helguson
Matches Started: 15
Substitute Appearances: 5
Minutes Played: 1404
Goals: 5
Assists: 2
Minutes per Goal: 281
Average Goals per Season: 14

For a comparison:

Kevin Phillips - At the same time for Birmingham and WBA
Matches Started: 84
Substitute Appearances: 23
Minutes Played: 7252
Goals: 52
Assists: 18
Minutes per Goal: 139
Average Goals per Season: 29

I think what these stats show is that our 3 strikers given a full season each will score maybe 40 between them but with all having only just returned from injuries are any of them fit enough to play 46, 90 minute matches? Also it is unlikely for them to all appear in the same line up. If each player averages 75% game time, which is more than Blackstock played in 2008/09 (68%) the number of goals will obviously drop by 25% as well. I think all 3strikers are good for goals and the stats show that but if injury reoccur than the number of goals dramatically drops.