Rolling 6SN7's in VAC Phi 200 amplifiers

I've got a pair of the Phi 200 monoblocks.  Just wondering if folks have experience rolling 6SN7's in these wonderful amps?  I've got a bunch of 6SN7's, and I am just about to start testing them all.  I know that one should match the inner pair (between the pair members) as well as the outer pair.  But I don't know if the VAC 200's use both triodes in the 6SN7 or only one.  Anyone else have applicable knowledge here?  Also, which 6SN7's have sounded best in Phi 200's?

Thanks, Peter

PS - I do hear that the stock tubes are supposed to be quite good.