replacing LR stereo head unit

Hi all, went into Autobarn and Strathfield today looking at the Sony head unit.

Wasn't all that helpful to me. Both places reckon i won't be able to use my existing volume controls on the steering wheel. Spewin... so i am thinking i won't bother. Mind you the first place the guy wasn't really interested. He said that i should just unscrew the volume control and leave it off. The second the chick had no idea. She was reading off the box to tell me about the features..... "they both have a volume control" and "this one has a bigger screen" were the main things she could tell me. So i might ring up and ask a few questions next time. I had both kids with me (both under 4) so time in a shop with them without breaking something is short.

Maybe the way to go is leave the factory system and buy a MP3 player with a decent Hard drive and get a Fm modulator instead......

What do you reckon. ????