I'd probably go with the following:-
Primary master - 160GB Seagate
Primary Slave - Sony CD burner
Secondary master - Samsung Burner
Secondary slave - old HDD
The old Sony burner might still be good for CD burning at slow speeds.
Generally it's suggested here that Audio CDs are best at 16x & data CDs at 24x max.
Use quality media though & the easiest to obtain is Verbatim I guess.