if you ever upgrade the Mac, you can reuse the 160 later. I have a 160 in an iMac400. I think the formatting limit is something odd like 137GB, of which 128 or so is useable.
Or you could look at an ATA-6 IDE/RAID card (although that's more money) and then you can put whatever size you like in - one of my B&Ws is currently running a 120 and two RAIDed 300s (not very quietly mind)
The Rev A motherboard had some issue with the secondary IDE controller and i believe it's not recommended to run a slave drive of any size off it.
I like Seagate. Anything has to be better than the cruddy, unbelievably noisy IBMs the B&Ws shipped with