I got one of those hornet DEI alarms before. And it worked great except the shock sensor is very very touchy so I had to turn it almost all the way down.
If I were you I would get a 2 way. Whats the point in having an alarm if you never know when it goes off. Its not like anyone is going to go defend your car if they hear it going off. Just cross your fingers the jacker has no balls and bails after he trips the alarm.
Oh and DEI mounting brackets suck on 5thgens. The only place I could see to mount it is on the DS shock tower but the speaker is just tall enough to rub on the hood so you'll get a dent if you slam it down and the alignment is f**kd.