sorry, i misread your first post, i thought you HAD the stock blues and were planning to "upgrade" to greenbacks...
i'm by no means anything of an amp tinkerer, not even close, the closest i've got (so far...) is just doing some prelimenary reading (and even at that, i've forgotten much of it already...). the thing to remember is all the "high voltage! death! warning!" aspect to tinkering with amps.
that aside, i think the ones to have a look at are the capacitors in the tone stacks. different capacitors have different tones: (eg, mallorys are often used in marshall amps, orange drops in fenders,.... as far as i can remember)
there are good sites up on the net about this kind of thing,
www.ampmaker.co.uk is a good UK based source for parts,
www.18watt.com is more focused on marshall clones but is still a good source of information. i just reformatted the computer so my list of links is gone unfortunately.
there are many people around the web more knowledgeable on this topic than myself, and i can't really give any specific advice. i would just say, read around a bit, and if you're semi-serious about changing a few components, having the amp's schematic will help a lot. at the end of the day, i only made the post above to make you aware of the fact that there are more cost-effective ways to improve your tone (guitar geek cliche phrase alert!) than changing speakers. (which doesn't mean changing speakers wont improve your tone; it will, it's just more expensive).
confused?
