low gain VTA board capacitor values

I know this has been discussed at length in the past (ad nauseum, with electronic theory ), but what is the value range suitable for the Interstage caps (C1 & C2 ) in µF? I know they are to be 400 volt rated and the parts list calls for 0.10 µF, but do they have range similar to the coupling capacitors, C5-C8?

Thanks, Jeff

At one time I did frequency response calculations with the low-gain cap schematic values and found they were spot on to provide decent lows without being too much. I'm sure 0.22uF would work OK as well in a pinch. But the larger the coupling cap value the closer you are to passing signals close to DC and can throw off bias of the next stage until these unwanted ultra-low excursions settle. This is known as blocking distortion if large enough to cut off the next stage. The larger the cap value the longer it takes near DC offsets to settle back to equilibrium. On the opposite end too low a cap value will limit low frequency response. I like a circuit -3dB response around 10 to 15Hz but that is just my preference.

I'm sure Bob has tried other values and can comment about viability in this circuit.

Thanks arledgc and Bob for your replies.  Every time I delve into this forum I learn something new or my ancient electronic training comes roaring back!  

My 2008 VTA ST70 is now sporting a low-gain CCS driver board.  I used 0.22µF PIO Russian couplers.  I left the interstage caps 0.10µF.  Everything sounding fine.  I'll give it the 100-200 hour break-in on the capacitors and maybe start some tube rolling.  I'm starting with clear top GEs; they're economical (for now!) and sound good.  

Thanks again,

Jeff