For the Amp 1 I would go for a transformer of 200VA or upwards
with outputs of about 0-22Vac,0-22Vac
The input for the 5V supply you can get from your positive input rail
You should be able to find something close to this available to you somewhere locally I would have thought . As long as the output oltages are not much higher that should be OK.
Yes the heatsinking is more than enough . Ive got fairly sensitive Mission 763 speakers so I havnt turned it up any where near the top.
Jackson Browne on it now is not even making the case feel warm AT ALL
My impression of it so far--
Well I liked my modified Sonic Impact. When i first plugged the amp1b in to some cheap speakers I thought "AHHH I think this is going to be good"
And I think it is .I havnt got the experience of others, with a huge variety of different kit but i do know that there is loads more detail than anything else Ive heard. I think I like what Ive seen described as Its rather clinical sound.
I modified /increased most of the electrolytics which improved the bass a bit further.
One final remark I find that you can play it quietly and not feel you are missing loads of the music which I am sure must be a real compliment.
Not an expert just a happy customer