Why? Would he even see a difference?
At 1024x768? It depends. In Crysis, HD 4670 gets 60 fps and 9500GT 30 fps. That one you'd notice. http://www.anandtech.com/video/showdoc.aspx?i=3405&p=7&cp=4
In less demanding games, yeah, all 5 of those cards would do nicely.
I totally agree with you he should get a new monitor ASAP, by the way.
Why HD 4670 before 9600GT now - that was the more difficult choice. He mentioned racing games, and I remember reading that those tend to favor ATI cards. For example the HD 4870 1GB totally humiliates the GTX 260 Core 216 in GRID (http://www.anandtech.com/video/showdoc.aspx?i=3415&p=7
), when in fact the GTX 260 Core 216 is just as good or even better that the HD 4870 1GB in lots of games.