PS - with the qualification that the hpijs driver gives lower quality printing for photographs than the original HP driver (or the Gurenprint which is also less good). Perhaps the 'force 32 bit printing' is ineffectual - anyway the colour range is restricted. Otherwise fine.
If you are unhappy with the quality of the HPIJS drivers, and you have a Leopard DVD laying around, you can install the drivers off of that, since it included drivers for your Deskjet 9300. That being said, you will need the '32-bit' workaround for full functionality, but that has nothing to do with the print quality.
In fact I used the HP (as opposed to Apple) drivers with Leopard - because they were better quality. HP say these will not work with 10.6.
An alternative solution for me is to have an older Leopard machine set up on the network - printing to the printer (which is on an Airport Express unit) from this is fine, and I have the ARD master software on my machine. Clumsy but OK for occasional use!
The Gutenprint drivers Apple ships are completely separate from the HP drivers Apple ships. The official HP drivers were just updated, but the Gutenprint drivers have not been updated since Snow Leopard shipped.