Its a bit difficult to answer your question when you have "intentionally withheld" the imformation on your CD player, but nevertheless.
In my experience, the difference between compressed files and Lossless, is very clear even just listening through the iPod itself - it shouldn't need a highly resolving system to discern this difference (though I imagine the rest of your system is actually pretty resolving anyway). Likewise, when I had my iPod docked in an Arcam dock feeding an analogue signal to my amp, it was clearly inferior to my mid-price CD player and that was playing lossless files. I found the best way to listen to my iPod was through the Wadia 170i Transport which feeds a digital signal from the iPod to my outboard DAC via a digital jitter suppression device. In this context, the sound from the iPod was equal to the CD player with the same jitter reduction device and the same DAC. Please see my review of the Wadia 170i here on A'gon for more information.
If you can't hear the difference between the various sources you described, I wouldn't be looking to spend $2k to try and hear the difference - if you enjoy the sound of any of the combinations you already have, be happy and buy more music. :)
If you are fixed on upgrading your source, I would look at investing in a decent DAC (some outstanding ones at under $2k) which would provide a significant upgarde to your CD player and SB. Alternatively, the Wadia iTransport plus a decent DAC is another outstanding option but get a DAC that does its own internal jitter reduction.