Did you change any settings in BIOS when using Adaptec 1430SA for 7th drive?
I tried using PCI 1e card with 2 internal SATA ports (http://uk.startech.com/Cards-Adapters/HDD-Controllers/SATA-Cards/2-Port-PCI-Express-Internal-SATA-Controller-Card~PEXSATA22I) but it does not work.
I just check my PCI card has similar spec like yours one, but when system boots up if PCI card is added then it detects only drives connected to PCI card and none of the system HDD bays.
It was an Adaptec 1430SA, but I took it out and now have 6 drives. I use the custom BIOS, so none are in IDE mode. This forum is about unRAID, so of course I'm not running them in a RAID.