Rogue Audio Dark Upgrade.

Thanks guys for some very informative information plus tube suggestions.  I have several 12au7 to try but will need to search for 12AX7 or 5751 that don't break the bank.  Or wait a little while until prices return to normal.  Hopefully.  This is definitely where I'll start before any other upgrades.  

@charcoalchuck agreed that Rogue is a steal at the price point.  I've had some really nice tube amps and the ST-100 rates extremely high.  Not sure its at Audio Research Ref level but pretty close IMO. Referring to older Refs and not the newest series. 

@mulveling 

thanks for your insight on the dark upgrade.  i am on the fence about a stereo 100 basic or dark.