After lots of hair pulling/scratching and cursing at the inanimate object we call the computer, I was finally able to get all the optical drives recognized in CD-DVD Speed and InfoTool. It wasn't a Nero problem as I originally had posted here. It was a combination of BIOS version on the controller cards and drives placement.
Originally, I had bought 2 Silicon Image 0680A-based controller cards as shown here. Both came with BIOS version 3.2.10, which was the latest from Silicon Image's website. However, there was some conflict as only 4 out of the possible 8 drives on the controller cards could be recognized in CD-DVD Speed/InfoTool. Even after trying different PCI slots, same problem still. In addition, the 2 external 1394 drives wouldn't recognize either. From this thread, it seemed like the SIIG controller card would solve the problem. After examining the pictures of it, it was also based on the Silicon Image 0680A chipset. Yet, from SIIG's site, the BIOS version was 3.0.93, which was an older one. Thus, I downgraded both cards to that version and tried again. As a note, I had to use the BIOS upgrade tool from Silicon Image's site since it was a newer version ('04) than the one posted on SIIG's site ('02).
Thus, it was time to arrange the drives such that all would recognize and burst properly. The end results were (using a nForce3 250Gb chipset):
1) Eight drives must be connected to both controller cards, any less would cause two drives not get recognized in CD-DVD Speed/InfoTool.
2) Two drives must be connected as Primary Master and Slave, Secondary M & S caused some drives to not get recognized in CD-DVD Speed/InfoTool.
Originally, I was going to get a new nForce4-/RD580-based motherboard since it supports two IDE channels (four devices), but with this new finding, I may be able to get a nForce5-/RD600-based motherboard because it only supports one IDE channel (two devices).
Lastly, the Syba-branded RAID and NON-RAID cards are the same, just different BIOSes, since I bought one of each.
So here are the two screen captures.