How do you determine how much to spend on speakers

It should NEVER be a matter of money but a matter of preference and synergy.

Let me give you a real life example:

I'm fortunate enough to be friends with Larry who owns Hollywood Sound (Hollywood FL.) and sometimes we spend countless hours listening to music experimenting with all kinds of analog configurations.

To our ears, the unassuming Spiral Groove Canalis Anima ($3,250.00) driven by top of the line Rogue (Hera II/Apollo/Ares) sounded MUCH better that the likes of Aurumm Cantus Grand Supreme ($18,000.00), Sonics Allegria ($15,000.00), and Rega's RS-10s ($13,000.00).

Analog set ups:
Nottingham Dais
Townshend Rock 7
Well Tempered Amadeus GTA

Carts:
Lyra Etna and Kleos

If you listen to primarily rock music, don't get a set of speakers with ultra high detail resolution and spend the rest of your hobby time and savings tweaking with cables, amps and room treatments to soften the edge. Don't let your equipment change your music tastes.

Figure which sound you like. Focal, Wilson B&W, Thiel whatever . Then pick the model in your budget. Then spend more than you can afford on the next model

Kiko65-You make a great point! Not many of us consider the Rega RS-10/Sonics Allegria/ or AC-Grand Supreme value leaders at there price point! I'm sure the Spiral Groove monitor would NOT want to battle a $4300 ATC SCM 19v2(lol)!

Anyone who tells you to put most into your speakers is clueless. It all starts at the source. IF you have just a "decent" speaker, the source is what will make all the difference.