what impacts the sound quality more amp or pre-amp

My memory could be failing me on all this, I could be mistaken, but if I recall correctly the B&K's ST series, had a rather low input impedance, and a low V input sensitivity for full output. Both of which can make matching a tube pre to a bit tricky. Another concern might be the ability of the B&K's non + ST series of amps ability to handle 4 Ohm loads well.

The nominal impedance of the IIs was 8ohm with 4 minimum. I think the input impedance of the B&K amps was the odd 33.2 kohms (you really have to double check with B&K), the Mapletree get be set with 0-10db or 10-20db gain, so sensitivity should not be an issue, I do think the B&K amps had sensitivity of 1.4v, but should not be an issue with an active line stage.

The nominal impedance of the IIs was 8ohm with 4 minimum. I think the input impedance of the ST202 amps was 24 kohms, the Mapletree has 500ohm output impedance (should be OK)get be set with 0-10db or 10-20db gain, so sensitivity should not be an issue, I do think the B&K amps had sensitivity of 1.4v, but should not be an issue with an active line stage.

I checked my facts for the second posting.

It's hard to say. It really is all about components working well together. A relatively modest change in a system that contributes to better synergy can have a much greater effect than a more ambitious change that doesn't improve synergy.

One way you can be assured of a synergistic relationship between the preamp, interconnect and amplifier functions is to buy an integrated. Also, everything else being equal, you should expect better build quality and parts selection in a thousand dollar, single chassis integrated amplifier than a thousand dollar preamp, amp, interconnect combination.