I second the vote for the GFA-555II. As much progress as has been made in SS amps, you still need to spend a whole lot more that what a 555II sells for used to hear an appreciable improvement, IMHO.
But I'd also like to throw out the Thiel CS3.6. They are one of Thiel's longest running speakers, and the lack of a 3.7 on the market (yet!) indicates that they are having a difficult time improving on it (though I am sure that they will). It also falls into the camp of having to spend vastly more money on an equivalent product to hear any significant improvement. I have heard my 3.6's up against two sets of speakers in the $10-12k range, and the 3.6's held their own or bested them. Lastly, the 3.6's are a product that lets you hear, with intimate detail, the characteristics of your other gear. So, you can drive them with amps costing twice what the 3.6's sold for, and still hear all the nuances of those amps (or whatever other high dollar gear you might be auditioning).
But I'd also like to throw out the Thiel CS3.6. They are one of Thiel's longest running speakers, and the lack of a 3.7 on the market (yet!) indicates that they are having a difficult time improving on it (though I am sure that they will). It also falls into the camp of having to spend vastly more money on an equivalent product to hear any significant improvement. I have heard my 3.6's up against two sets of speakers in the $10-12k range, and the 3.6's held their own or bested them. Lastly, the 3.6's are a product that lets you hear, with intimate detail, the characteristics of your other gear. So, you can drive them with amps costing twice what the 3.6's sold for, and still hear all the nuances of those amps (or whatever other high dollar gear you might be auditioning).