The current radio is the HU-650 with CD/cassette. It's doing the typical thing where it jumps from station-to-station even if it is tuned to a strong station. As a side note, I have gone into the C-pillar and inspected the antenna connections. All is OK there, confirmed by connecting/disconnecting while the radio is on and the antenna appears to be working.

Also, the volume control is whacky - volume INCREASES when I turn it counterclockwise. Sometimes you have to spin, spin, spin the knob to get the volume to change. Almost like the FASTER you spin it, the better it works. AM reception is "fair" at best. Looking at the backside of a radio at the P-n-P, it looks like the volume and station selector controls are pretty much unserviceable.

So, to replace the radio with a brand new Volvo unit is cost prohibitive. Replacement with a used Volvo radio seems like a waste of money and energy, given the many complaints I've read about these things. So that brings me to the point of replacing it with an aftermarket unit.

There are trim panels and harness adaptors that allow you to install a standard DIN Kenwood or whatever radio you choose. If I go that route, what are the complications I can expect? ie, will the current built-in antenna work OK? Will the steering wheel controls still function? Is the car alarm integrated with the radio system in any way?

In a nut shell. I don't even know what I don't know. Have any of you tackled this before?