How much do I need to spend to get a preamp that sounds better than no preamp?

kosst_amojan
Like mrdecibel said, the perfect world doesn’t exist.

Don’t cheery pick mrD, a perfect world does exist if the impedance’s are good, low output and high input (>1:10 ratio), and in most cases they are.
Go away now, you are so annoying.

@georgehifi
Oh... I didn’t realize the typical amp input impedance was between 100kR and 250kR. I didn’t realize input transistors have no gate or base capacitance either. Ten to one is really more of a minimum, not the ideal. And since a passive is all over the map, that’s hardly a given ratio.
Can you just go away so I can stop correcting you? 
And by the way, I didn't cherry pick. My statement captured the essence of what he said. 

You really have lost it, as I said 10k pot has at worst output impedance of 2.5k, a 1:10 ratio of that is 25kohm, so any amp with >25kohm or higher input impedance will be fine 
Please go back to school or stay off the *****, it’s effecting you really bad, seek help.

@georgehifi 
Come on! You can't really believe that! Nobody building an amp with a 25kR input impedance has any intention of it being fed with a 1kR+ source! If your amp has that low an impedance it's certainly got BJT inputs and those take current to drive so you'd better have a pretty low source impedance. Degenerating the source with a few thousand ohms will absolutely color the sound more than a buffer.