the 7240S series is considered as the best allrounder at the moment. But please be aware that this is a Sata drive, so you might need an additional Sata controller (unless you have a reliable Sata controller onboard).
I would keep the Benq additionally and retire the Nec-3500.
Main advantage of a newer drive: better support of recent blank media. I doubt, it will improve the way you are using your drives. Burning "on the fly" is not recommended at all.