Leach amp caps' quality?

[PWatts]

Hi Guys,

I'm currently building a top-end Leach Amp, and I'd just like some comments on the audible impact of some components' quality. Everything I use has to be imported at expense, so I don't want to upgrade where it isn't worth it.

1) C7, 100nF feedback cap in parallel with 220uF C6. Currently I use an Evox-Rifa polycarbonate, is this sufficient or should I rather use Solen or even better?

2) C12, 100nF across Q7. Currently I use the same polycarbonate as for C6. Upgrading to 1uF as is often suggested is difficult if an axial cap is used, which will not join the board close to Q7. Should I just keep the polycarbonate / change it to a better quality 100nF polyprop / or bypass it with a quality 1uF axial at the solder side?

3) The widely recommended 1uF 'speedup' cap across R36. Any use going above Solen?

4) C17 & C18, 100nF in the protection circuit. Currently I have some AVX polyester ones which may be fast enough, but can change them to Bennic polypropylenes I have at hand. Any use going better?

5) C19 & C20, 10nF in parallel with 470R R39 & R40 respectively. I currently have some Wima polyester ones, will upgrading to Wima polyprop benefit? Polystyrene or other nice caps have axial leads and will be dificult to fit close to the current position.

6) C25 Zobel cap, 100nF. As it is used well above the audible range standard polyprop like Dayton/Solen should be OK?

Thanks,
Pierre