harman kardon drive+play issues

ok so here's the story i purchased a 2005 subaru legacy gt limited a few months ago and the first thing i wanted to do was integrate my ipod into the factory sound system. Now for those of you who don't know, this car has auto climate controls so i cannot replace the radio so this is not an option for me. So there is a member of my legacygt.com forums who had a company manufacture a aux input piece which daisy chains the cd changer cable inside the radio and allow a 3.5mm jack to be plugged in for any device. So i purchased this piece along with a ipod plug to 3.5mm cable and a GLI for any ground noise. Work fine sounded good. So then i found a great deal on a harman kardon drive+play on buy.com for $20! Couldn't pass it up so i got it, installed, hated it. The sound quality was horrible, after tearing my hair out i removed the GLI and the sound got better but still not a whole lot of bass response. My question is why is this? Aux in to aux out should be the best option but sound is horrible. The piece i ordered obviously works cause it sounds good with just a mini-jack and the d+p i swapped out to rule out a bad unit but the same issues. I even installed in into my wifes nissan sentra which has a dedicated aux in and it sounds great. Any ideas i love the ease of use with d+p and don't want to get rid of it. I'm even contimplated buying a jl audio cleansweep and 5 channel amp and going all out but rather not. Any ideas would be appreciated sorry for the long story.

here at my shop we have tons of sound quality issues with the drive and play and stopped using them a while ago.

now as far as changing the radio out it is possible all you need is these parts

Metra  70-8901 harness

and

Metra  99-8901 dash kit and thats it

Thanks for the info, do you have any ideas on differents units that may work better? Also that kit is for manual heat controls i have auto and it won't work. I can mount the radio in the pocket above the center console but not a huge fan of having 2 radio i think it looks wierd.