I don't know what to tell you about the parts. The correct values are the correct values. How "different" it will sound using incorrect values I cannot say. It certainly won't be right but how wrong it will be I couldn't guess.
Cap break in can take 300 hours or more, and yes you can get wild swings even in the same session. The only answer is to keep playing them. Inductors are not nearly as bad as caps about break in but I have heard the odd moments can sometimes be attributed to them.
As far as amps go it depends on your budget. Get the most current you can get for your dollar and you should be OK. There are so many options, just do a search here and read some of the posts to see what people like.
It's all about the music...