There is NO SUCH THING as a "foolproof" alarm. The best thing an alarm can do, and the only thing you should expect it to, is a fuel cutoff so your whole car doesn't get taken. It will not protect car audio.
The more agressivly you install it to prevent theft, the more damage they will cause when they do take it. For examle: my deck was screwed in last time, they just ripped my whole dash open with a prybar instead.
2-Way is great, but you can't tell me your always within range of it, or that it will work in an old stone building, or that you'll even hear the 4 beeps.
People don't pay attention to car alarms anymore.
Do yourself a favor and keep the faceplate of your deck off and out of the car, and don't flaunt what you have. Park in high traffic areas, where many people would pass, or atleast somone would pass every 10 minutes. Th alarm is a deternt.... the more juvenille theifs will think twice. Pros won't bat an eyelash; slim jim door, pull open, pop hood, gra siren, rip it off car, drop hood, remove deck, pop trunk, clean it out, gone <10 minutes.