What would be the fastest Athlon XP processor I could get and still use an SK-7 or SLK-800 and panaflo at 12 volts and 7 volts.
The case has minimal airflow. Basically only a panaflo in the PSU and no case fans. I could add a case fan if needed.
Welcome Jonestown, I can't answer your 1st question, but I can tell you that having an exhaust fan will help you run the HS fan at a lower speed while keeping your CPU temps the same.
Also, I have an L1A in an Antec 300 watt PP303X PSU. Can I run that fan at 7 volts and the PSU still be cool enough. Also, should the fan be sucking air out of the PSU, or blowing into the PSU?
Does the pp303x have a thermal control fan circuit? What other components do you have. To be on the safe side, I'd say make sure you have a case fan before running the L1A @ 7V. To be even safer (and/or to allow for 5V operation) I'd duct in fresh cool air directly from the outside. See my duct as an example: http://forums.silentpcreview.com//viewtopic.php?t=2842