That said, back when I was much younger, we were all lusting after getting a Marshall. In my small group of guitar-playing buddies, the other guitarist in my band was the first to get one. He bought a used early 70's Super Lead 100 watt head, shows up the night of a gig with it, and proceeds to hook it up to the speakers in his Super Reverb combo, and it sounded like absolute azz! He thought something was wrong with it.
I can *soo* much relate to that story. Wasn't exactly Marshall tones I was after, but I had *no* idea about the relevance of speakers for a pretty long time during my "career". And unlike your mate, in the town where I grew up there were no folks telling you that you needed a particular cab or speaker to get the most out of whatever amps (and that was quite some time before the internet was a thing for mere mortals), so I also built randomly sized cabs with randomly purchased speakers, most of them sounding horrible. Sometimes I accounted the not-too-shiny sound to the amps, so the amps were sold - just to find out the replacements would sound as horrible. But as they sounded horrible differently, I still didn't realize it was up to the speakers.
Fortunately, at one point in time, I bought a Boogie Caliber 50 and built a clone of their 2x12 half slanted cabs (those with the open back top and Thiele/Small ported bottoms, originals were more expensive than the amp...) with pretty similar sounding Celestion speakers in them (don't remember exactly, which ones they were but at least they sounded great and close to the Black Shadows in the original I had borrowed for the cloning thing and comparison). Still didn't exactly know how much my then great sound was about the speakers, but at least I could call it a day for some years - and all other cabs I bought ever since (and before aquiring more knowledge) have been lucky numbers.
My most drastic personal eye opener in terms of speaker importance happened quite some years later. I sort of blindly bought one of those red knob "The Twins" because I couldn't resist that offer (price was a joke). Clean sound was ok (sometimes great), anything else sounded completely like @ss. Always thought it was a bad buy, especially because I often heard comments such as "Ouch, the red knob Fender series, only complete tools would buy those!" Then fortunately someone recommended I should just connect my Mesa clone cab instead - and *WOO-f***ing-OOW*, I could hardly believe it. Turned that horribly gnarly, bite-y, speaker beaming, ear torturing mess into what I still think of being at least the second best pedal platform I ever owned. Really, I couldn't believe the difference. Plugged between the internal speakers and my cab like a hundred times, that's how stunned I was.
Finally slapped some decent speakers (an aged V30 and a Peavey Sheffield I had in the Mesa clone for whatever reasons) into that Fender and it was all glorious.
Only took me around 1.5 decades to understand the importance of speakers...
