Sonic Frontiers pre-amps

Anybody out there fmaillar with the Sonic Frontiers line of pre-amps?Has a phase inversion feature I'd like and have found only on Bryston and BAT equipment.But wondering if anybody can tell me the difference pbetween the SFS series and the Model 1,2 and 3 that came out afterwards.Also has anybody compared the cost to quality ratios of the Model 1,Model 2 and Model 3?More tube and bigger power supplies as one steps up.I am inclined to think that latter pre-amps were better but unsure of this.Know that Anthem/Parts connection gives support to these pre-amps but wondering if anybody has sent there equipment for upgrades to somebody else.I wonder why the line which was very highly regarded (think SFS-2 was class A in stereophile) went south.But it's a pretty competitive marketplace and perhaps there was just more money to be made with the more modest Anthem line.Anybody with any info it would be much appreciated.Bryston just does not flip my switches since it's SS and BAT well seems like better value might be had since prices are lower for this older line of requipment.Thinking of mating it with a Krell KPA SS phono stage though again if anybody has or has had the phono stage I'd like to hear about them.Again any insights appreciated.
Thanks
Chazz