Okay, how about this scenario:
Remove the checkbox; add a button that says "Select these now
(Recommended)". When you press it the packages are selected and the
contents of the text box are replaced with the status of those changes
(e.g. "selecting foomatic-1.2.3-1..." but the wizard stays on the same
page.
If a user just presses Next, they get a popup saying "You should really
install these before continuing, do you want me to do that?
Y/N/Cancel" Yes would apply and move on to installation. Cancel would
dismiss the popup and leave them at the same wizard page with no
change. No would present a second popup saying "Are you really sure you
want to continue without selecting? Y/N" to eliminate the chance of a
user in a hurry selecting the wrong thing.