Great post! Welcome to the "Brotherhood". For me,the biggest selling point for any boombox is it having a line-in.My boxes come to work with me mostly to play my Ipod through the line input.Maybe I just expect less than yourself but I'm quite satisfied with the cheap cables and high bit rate MP3s.This has been a regular practice for me during the busy work hours of my day at work over the past few years.
I carry a tackle box with a complete selection of cables to cover all the different jack types I've encountered.There's an inexpensive phono to line converter that's been a great help for boxes having only phono capability.At times I will hook several boxes up with a splitter to hear the effect.Since line-ins all have different sensitivities (sometimes as a result of simply needing to be cleaned) I also carry the standard version of the Boostaroo headphone amp to compensate.
My player of choice is a 1st Gen. Ipod Touch.I chose it because of its versatility and the variety of accessories available for it.The most useful has been the Sendstation Pocket Dock.This bypasses the volume control on the Ipod so I don't have to mess with it. It was a pleasant surprise when I finally figured out that it allows through the EQ settings to the box.My most used preset is "Treble Boost".
I've never been very happy with FM transmitters.The CCrane FM transmitter is probably the most powerful consumer model.There's even a very simple hack to increase its sensitivity with surprising results.
Unfortunately the screen of mine lost its digits from sitting in the heat.This makes it a bit of a hassle to set up.No matter because there's just nothing that feels better than being able to use all the built in capabilities and features of a classic box.
btw-Thanks for the soundcheck tip.I never knew what that was for.I've been normalizing everything sent to my Ipod with a program called MP3Gain.