HOUSEBOAT SYSTEM

What are the restrictions?

One idea would be to create a hard drive system. Then you could have all your music on your boat w/o bringing your cds along. If you have a lap top you can just buy an external drive. If you don't, you could buy a mac mini for not much money.

If you're looking for an un-typical car system, there's a tube car stereo (pioneer?) that looks interesting. I haven't heard it. Gets fm and plays cds.

looks as though you could get by without a preamp. If not go passive or battery operated. I thing there are some battery operated amps. Ironically and I have not tried this but most components are stepping the voltage down to car battery range any way. You could have an amp modified for straight in 12 volt dc.
good luck

If your concerns are about space, why not look at the high end active speakers like those by ATC. This would eliminate the need for an amp, while maintaining a high-end sound. I've only heard a pair of their monitors, but the sound was very impressive. Pricey if you get into the bigger boxes. An SCM 20 montior is around $3500, while the SCM 100 3-way is up at $11K. If you pair that off with a front-end player with a good gain control (not sure if your Sony has that) you won't need a preamp. I'd go with a laptop computer system as Kublakhan suggests, along with a USB DAC like the Benchmark. RIP your file to WAV or Apple Lossless and you'll be cookin' with gas!

Marco