4 Channel Tube Amp

My first question should be is this an appropriate forum for the beginner just trying to get in the game. Referring me to other reading or forums would be great also.

I currently have a 4 channel set up which, because of the layout of my apartment really works well for me. I currently have an HK3600 integrated amp that feeds two sets of stereo speakers and a sub-woofer.

I'm itching to move beyond the integrated amp - preferably to an entry level tube amp like a dynaco st-70 or something priced similarly (I'd need pre at this point also).

My question is would I have to sacrifice the 4 channel + sub set up if I did get a tube amp? I don't think I've ever seen one that supports two sets of stereo speakers. Is there some way to split the signal after the amp? Is that defeating the purpose of a quality amplifier?

I need a lesson in high end stereo topology!
I think your only option is going to two stereo tube amps. If everything is in the same room I would think a 5.1 system would be a better fit for you. Two amps and a powered sub.
And I'd hope you lived in a cold climate so you wouldn't cook.

Do you know if your current speakers would like tubes? Would you be willing to get down to a single, maybe more tube friendly, pair of speakers?
Here is where my naiveté comes in. I don't know if my speakers are tube friendly. They are Polk Audio Monitor 60's. Like I said I'm playing in the shallow end. I don't think I'd be able to swing two amps out of the gate but I would be willing to drive just 1 pair of speakers to try out the tube experience.
Out of these specs, what would I be looking for in terms of amp friendliness?
Overall Frequency Response 38Hz - 25kHz
Lower -3dB Limit 48Hz
Upper -3dB Limit 24kHz
Nominal Impedance 8 ohms
Recommended Amplifier Power 20 - 200 w/channel
Efficiency 90 dB
Crossover 2.25kH, second order high and low pass
Inputs Dual (bi-amp) 5 way binding posts
Butler Audio makes 2-3-and 5 ch tube amps.
The one spec speaker manufacturers NEVER divulge, but can be found by test in a lab is very important to tube 'friendliness'
That is: Phase Angle vs frequency.
In any reactive load.....capacitive or inductive voltage and current are out of sync. The amount of out of sync is measured in degrees.

I don't know about your Polk speakers.

In general, large swings in impedance and in phase angle are not fun for tubes to drive.
Stereophile may have tested your speakers, in which case the data will be available.
Impedance and sensitivity are nice to know, but only when you know the 3rd leg can you make an educated guess.