All right, I finally got over to CompUSA and bought the Adaptec card. It is Adaptec Model #ASH-1233 "Ultra ATA/133" controller card. It is based on the Sil680 chip--I took a pic before I installed it (below) so you all could see the silkscreening on the chip.
The card is a bit overpriced at $49 U.S. at CompUSA, but OTOH, it is a basic, non-RAID card that shouldn't get you into trouble. (Plus if it goes bad, I have 21 days to take it back--locally, no return shipping costs. ) Some of the cards apparently were shipped w/a sticker on them that said something about RAID, but Adaptec's knowledge base specifically says that the card does not do RAID. (Mine doesn't have that sticker.) Which is good news for those of us who only want to add more burners--also adding RAID can gum up the works. Especially if you--like me--already have an onboard RAID controller running. And we certainly don't need RAID for burners!
A couple of notes: I had planned to just install the card, make sure it booted w/the system, install the drivers, etc. And then go ahead and order my new burners. But it hung at the point where the card's BIOS loaded--my experience w/Adaptec cards is that it was probably looking for a drive, and was darn sure not going to boot until it found one. So I took my LG 4163 off the onboard IDE controller, changed it to "master", hooked it up to the Adaptec, and the system booted like a charm. The card definitely wants at least one drive hooked up to it, before it will play w/you.
I used CD Speed to burn a data disk, then did a disk quality check. Seemed like everything went okay. I plan to order a couple new drives to put on this card, and put the LG back on the mobo's IDE controller. In the meantime, I'll burn a couple of movies, to see how it performs. Will keep you posted.