Pani,
You have two of the best circuit designers I am aware of (Ralph and Lynn) tell you that tubes are not going to deliver what you are looking for with your hard to drive speakers. I'd believe them.
Class D GnFETs are one very good option (that I have no experience with), but I'd also make a phone call to Doug Dale at CODA regarding his Class A solid state high current amplifiers. He has the newest version of the System 150 WPC (100 WPC Class A) and System 250 WPC (200 WPC Class A) coming into production soon....his contact information can be found on the CODA website.
Since they are new products I of course have not heard them. I do own their baby brother the S5.5, and it is an absolutely brilliant amplifier with performance I never thought I'd be able to achieve in a "mid/hi fi" system.