I'd actually recommend that you go straight to DSP. A pair of 24-bit 3100s (similar size to your existing) or better still 24-bit DSP5ks can be had for relatively little money, especially as you have other kit to sell to fund this.
Even 18-bit DSPs will not be too much of an issue if you are only listening to CDs and no high rez music, but you will then want to upgrade them as well..
This is another good alternative, with a pair of DSP5000s, you would be able to stream straight* into them; DSP speakers have full pre-amp functionality, crossovers and power amps coupled directly to the drive units.
If you wish to stay 2 channel with this system, it would be far cheaper than a 568.2 and 557.
*depending on what you use to stream; the inputs on the DSP loudspeakers is electrical SPDIF, things like a Apple Airport Express use optical SPDIF and would need to go through a converter like an M-Audio CO2 or even a Meridian 518.
All the best,
Steve.