Hey - I just got my 2004 325cic, deliberated about the hardtop but opted not to go with it. My dealer told me there usually isn't a problem with color match for after-orders. Everyone I spoke to who had actually seen the hard top installed said the car looks kinda funky with it on. Perhaps, more importantly in light of your step-mom's age, it takes two people to lift it on and off, storage can be a problem as can scratching the top and/or vehicle while taking it on and off.
I'm in Florida so cold/snowfall isn't really a problem. When the top is up the ride is really quiet, and I'm glad I didn't end up ordering the hardshell (and shelling out the $2000).
I spent the extra dough for the HK sound system and most glad I did. The auto control volume thing is great, and I can notice a big difference in sound quality over my girlfriends 525i, which only has the stock stereo system.
A couple things are a little strange, though - the display doesn't give much info about the currently playing track. It tells you what number song is playing, but it won't show the time remaining or even time elapsed. A minor point, but still... Also, the system has great bass, especially considering there is no subwoofer, but maybe its too great - when I turn it up some, the bass rocks so hard the disc begins to skip. Me no likey that.
If cost is a consideration for your step-mom, tell her skip the hardtop, go with premium and sport package, and the HK sound system. As long as she doesn't live in blizzard conditions, she should do fine with the soft-top (and the cool luxury of one-touch lowering and raising the top that comes with the premium package).