benq 161i will do. And its the cheapest at ~$150
external burners require usb2.0 to run.
An external casing cost about $70 to $90 depending on the chipset as well as whether it had firewire or not. Firewire is basically similar to USB in that it transfer data, but because it can transfer a lot more data, it is usually used for video transfer. So external casing that have usb 2.0 and firewire can truly burn at 16x and perhaps more( but so far, no higher speed), while those on usb 2.0 can max out at 12x only.
However, these devices are more for the hardware inclined because they might not work with certain motherboards, have power problems etc, etc. Then u have to factor in the cost of the Dvd writer which adds another $90- to $150.
I do not recommend this unless u need that cutting edge technology.
. Upgrade? from 16x to 24x? it will probably save u 3 mins of burning time..and in the process, u might get more coasters because of burning at high speed.
So just buy a simple ready made external burner and it can last quite a few years already.