$300 can easily get you a good alarm.
I picked up a "cyber alarm" from strathfeild which happens to be the same alarm as the "viper" from autobarn, both of which are made by www.visionalarms.com.au
who supply the alarms for the high end Fords including the T3's.
The one I got ( http://www.visionalarms.com.au/1800.html
)is one stage below the ones fitted to fords, but it is still pretty damn good. Lots of features and programmable too.
With a bit of haggling and playing autobarn and strathfeild against eachother, I got it for $199 when RRP was $350.
Dont worry if you dont like the look of the keyfobs, strathfeild have a different style to what is on the website, and autobarn have it different again. So you can have a bit of a selection.