How do you determine how much to spend on speakers

Speakers are the last item on the musical chain; however, the golden rule "garbage in and garbage out" is absolutely correct.
You cannot correct anything wrong to begin with.
For the last 30 years, I have listen to system sometimes cost more than a house (over 300,000) and sound like you want to it off in less than 15 minutes. At other times, I can listen to a system with no more than $5,000 altogether and enjoy every minute of it.
TRUST YOUR EARS, a system is a combination of all the components and if you want to listen to it for more and more; no listener fatigue and that is a good system.
Something happens to the allotment of the speakers.
Think about a system with a 100,000 speakers yet hook up to a $200 receiver; will you say this is a good system?
Go figure.

I didn't read this whole thread because I'm not a masochist. But I read Robert Harley's book and he advised spending 50% on speakers. I found myself unable to do that, because the speakers I liked didn't cost that much money, and my analog and digital front ends both ended up costing in the ballpark of my speakers. If I were to look at my current system breakdown, speakers have ended up being about 20-25% of total system cost. I would imagine a number of people shoot for 50%, but end up in a similar situation when they find that they don't want to shortchange the good equipment in their systems with bad equipment. I agree with Robertwolfee and others who have said this: "trust your ears." And don't spend more than you can comfortably afford at any given time.

I have never understood the relevance of the phrase "garbage in, garbage out" in these types of discussions. If a $1000 to $1500 integrated amp is producing "garbage out", then you were ripped off. The THD on a Yamaha a-s1000 integrated, which sells for around $1200 is less than 0.02%. The only thing that a more expensive amp might do is play louder. Louder, not cleaner.

The 'Garbage In Garbage Out' axiom is I believe directed towards the source componet.

Mentioned earlier you CANNOT fix, repair, replace or get back lost digital or analog data once it has been sent upstream to the next component in the signal chain. In fact the amplification that occurs in each component is an enlargement, not of the original signal, but of the signal it receives. If there is dirt, distortion, or grain, these flaws are MULTIPLIED with each enlargement. By the time the musical signal gets to the speakers these flaws have been multiplied several thousand times. This is why the source is the most important part of any system.

That signal is then converted to another format once it reaches the DAC, run through a filter and a buffer, several chips, then converted to analog where it’s run through another filter. That signal then travels in the analog domain through several thousand parts in a preamplifier and amplifier in the analog domain before being sent to the speakers.

No matter how good, how expensive, or how many claims of magic the back end components in your audio system may boast, the best signal they will ever see is what comes from your source.

As you can see from the above, there is very little hope that any system will ever deliver what was recorded to the "Master Tape" or produce what was heard in the studio.

Put your dollars into best electronics, upgrade speakers later. That way you'll always get the most out of your speakers - they can't fix a poor signal from source components and/or preamp.