I know it's not a tube solution, but I'd suggest trying out a transformer-based passive linestage (aka TVC) like the Bent Audio NOH no matter which power amp you decide on. Mine works sublime, transparent magic whether it's driving my Sugden AU51p SS amp or my Wavelength 300B SETs.
Both the amps you mention have an input sensitivity sufficiently high to make this a pretty sure-fire solution. I've compared it to the Sim P-5, and the NOH lets quite a bit more music through.
Both the amps you mention have an input sensitivity sufficiently high to make this a pretty sure-fire solution. I've compared it to the Sim P-5, and the NOH lets quite a bit more music through.