Extra after market stereo on mazda 3?

I seen on ebay a dashboard mount for using an extra after market stereo on your mazda 3 so you dont have to remove or modify the original stereo and it seems like a very attractive option that i been looking for so i can use an ipod stereo that features album art and i seen the reviews of the alpine ida-x100 and i think im going for it but i wanted to know if its possible to use this alpine and my factory stereo at the same time, is it possible to connec the alpine to the aux input or how does it work if it really does?

i have some pics so anyone have any idea if you could use them both at the same time?

no.