I've been formulating a plan for a commentary set-up on the gospels. I already have EBC: that's Carson on Matthew; Wessel on Mark; Liefeld on Luke and Tenney on John. My companion volumes for each of the gospels will be: Keener on Matthew; Witherington on Mark; Bock on Luke and Carson on John. I've already acquired Witherington and Carson. On Matthew, I did consider Hagner (Word Biblical) and the Davies/Allison monstrous tome (International Critical), but the latter's probably a bit too technical for ministry. Since I have Carson already, I went for Keener over Hagner. On Luke, it was either Bock or Joel Green; I've decided for Bock. Neither Keener or Bock could be described as cheap, but they are both very thick. Keener's is massive and would be excellent to hold down your car accelerator if you wanted to fake your own death by driving your car off a cliff whilst jumping clear at the last possible moment (kind of Bourne Identity, but in a Biblical Studies setting). Bock's is two volumes, so not quite so handy for that kind of thing - special ops theologians take note.