"My monitors are 89db @ 7ohms,though if I added a powered sub wouldn't that compensate a little power distribution-wise?"
Not unless you included some type of "high-pass" filter before the amp to block low frequencies from reaching it. Even then, it may not work depending on the impedance curve of your speakers.
Bottom line, your speakers probably were not designed to be used with low-powered SET amps, so don't waste your energy trying doing so. That would be an attempt to use the wrong tool for a specific job.
The goal is not have a system that simply works, but to have one that works to the best of it's abilities. Your speakers will not provide that with lower-powered SETs.
On the other hand, Art Audio's 16wpc Carissa (845 tube), or even better, 20/32wpc Jota (depending on output tube) probably will drive your speakers fairly well. But, they do not have the same "magic" of the lower powered offerings. Although, they do have their own benefits in the area of lushness and slam, respectively. Either of these amps could potentially make a fantastic match with your current speakers.
Please heed the advice people are trying giving you here, low-power SET systems requirement far more planning and understanding than normal high power setups. There are no shortcuts, there are no free lunches.
