When modding amps is it reccommended to use metal film componets like it is with effects pedals or does it really matter? Also what wattage of resistors do I need to use?

I plan on doing this mod to my jcm 800 4210. http://music-electronics-forum.com/showthread.php?t=5107 . does anyone know anything about it or thinks it looks very good?
Thanks Alex
Don't recommend it. I don't know about your amp, but a lot of electronic devices are factory-made PCB's. Resistors used in factories are not our conventional resistors, but flat resistors with solder pads instead of leads. They would be hard to replace with lead resistors. It probably won't change the sound a ton anyway, and you would be risking messing up your amp.
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caps are caps...just get a high enough voltage rating and be done with it... I personally never heard any difference

resitors.... depends on where they're being used. As most 2/3 of the preamp is regular half watt ones but theres a couple of big ass ones around the power tubes and in the power supply sections
Thanks seljer! Does it I am only making changes to the preamp section so what voltage do you think I would need from the caps? Also does it matter if I use metal film or carbon resistors?
Caps are not all the same. The different dielectrics have different properties that can affect capacitance depending on the frequency. Just use polypropylene, they'll be fine. 600V caps will be enough for just about everything.

The resistors won't matter as much as the capacitors. Audiophiles swear by metal films, but I can't hear much of a difference between them and carbon comps.