Ok, well I think the 3 piece boxes are probably going to list strongly in your pole as they generally don't pull the big $$$$s plus they tend to sound better to the due to the separate speaker cabinets.
The Yamaha PC-8 is the best under $500 Boombox I've heard for bass, treble and general listenability. The Panasonic RX-DT680 would be my second choice as it also sounds great but the 90s build quality drops it to second place in my list.
Incidently, both boxes did need work and as such, were EBay cheapies. The important thing is that they ended up performing well after some standard maintenance. Dispite how 'mint' a box is, most need at least a little TLC to work right.
James...