but you get what you pay for.
That I can't agree with. You NEVER get what you pay for (and this can be applied to just about everything - but new electronics in particular). An incredible 70's amp for $50 or a pretty good amp from today for $500 or more. I think I'll go with the 70's one.
Why - do you forget to take your purchases home with you?
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I'm not sure what your definition of quality is (as in the type of 'sound' that you prefer), but $50 won't buy much of a vintage tube amp. Barring sweet deals at Granny's garage sale, it's easy to spend hundreds of dollars on a good ol' McIntosh or Marantz amp. Now I'm not an extremely well versed and knowledgeable audiophile, so take my thoughts with a grain of salt (they taste better that way too). Perhaps there are better options out there that I'm overlooking.
With regards to more modern equipment, there are plenty of cd players, amps, speakers, etc. that won't break the bank but will handily outperform nearly all vintage equipment. The biggest exception applies to tube amps, as they haven't really changed much over the years. Luckily, my tastes are pretty modest and I'm satisfied with solid state amps.