Which Solid State amplifier would you recommend for my budget?

60 watt monoblocks were plenty strong for my Acoustats. Currently very happy with an S300 after replacing the welded woofers with 4 ohm versions.

I have never got around to measuring the current sensitivity.

I think it will come down to what character you are looking for. I think you have identified some amps with “the right stuff” for speakers requiring high current. Given you have a Conrad Johnson preamp I would think the Krell would be a great match. Doing some reading I would pick the Rowland Model 5 second. 
 

While I was a Threshold fan 40 years ago, once Pass left, less so. 

+1 @ghdprentice What sound characteristics are most important to you and what specific improvements are you looking for over what you have now?

Also look at Belles. 

I have only used tube amps with Acoustats. I currently have their Servo amps that have been modded, but still put out 40 watts each and that’s more than enough!

All the best.