Sunfire classic tube pre amp, Difference between Signature 97’ and non Sig. 01’ models.

I’ve been looking far and wide to find technical info on what mods were done on the  original  year model 97’ Sunfire Signature classic tube pre amp  to the Sunfire non signature 01’ classic tube pre amp  which I own both , and  the later models on what Bob had done to them in bettering the sound quality. The 97 Sunfire Signature classic has a phono Board, and the Sunfire 01’  “ non” signature  has a remote, I was going to combined the phone board and Remote board to one Amp, But I’m not really sure which of the two is overall the better amp. I’ve read that he better the power supply and changes in the quality of the electronics , Caps, added resistors, etc. as the years went on, But I’ve been unable to really find out what was technically done to them through the years to the final productions, But kept reading that there were improvements along the way, and that in the final years of production the Sunfire Signature Models combined the better electronics and improvements, But I don’t believe he made another Sunfire Signature classic tube preamp after the original year of 97’ , at least I havn’t seen one. I love the look and sound of the Sunfire pre amp, and would like to keep it in the system and would really appreciate any help and information on how to Lower the noise level and better the sound quality as I’ve read was done in the latter years. I  greatly appreciate any info and help on this
There is very little information out there on sunfire.
Thanks