ok i m bored, and since noone is replying this thread.. i m just gonna bash it... LOL..
ok.... maybe i m old fashioned, but try to find a system that is FM/FM 2-way.... FM/AM is not a really good system, as you can send it but not knowing of what you are receiving of what you've sent is a headache!! , always research what you wanna buy for your 6.... and prob, for safety, you'd want a code hopping for the alarm.... if you want to install if urself, i would vote against that!! always find a shop that is very reputable installing alarm systems that wouldnt mess up ur ECU( i know ppl who got their engine replaced cz of the shops' job) !!!
all the systems are fine, but finding a reputable shop that can install them properly is important !! EVERY systems are good, but the installation is important !! anyway... just my 0.02... good luck