One year down, two to go. What's the longest you have saved for one component?

gavman, so, you're doing all this for exercise?  ;)

What an interesting situation, and obviously unique one at that! You are in the rare position of doing what you described without endangering your livelihood, it seems. It is fascinating to hear about audiophiles' personal lives; they are as varied and complex, with as many nuances as the systems they build. It's also interesting to see how personal experience and preference plays into the build process, as a search for a particular outcome. 

I do know of at least one instance where a person was highly imbalanced in life and was spending inordinately on equipment, which caused a great deal of pain and trouble. But, you seem to be on a grand adventure, leveraging your strengths to achieve unusual outcomes. Kudos! 

bob540 is also to be commended, and looking at the fiscal challenges he has had, a $7K+ system is quite an accomplishment! It's a definite labor of love, and I hope you enjoy it thoroughly! Contentment makes one happy, not money.  :) 

I share this not as a harsh, unkind comment, but as a clear analysis in the hopes that the OP, or someone else who might struggle with such things can gain some direction: 

It is not "saving up" to go into a payment plan; quite the opposite. It's going into debt, obtaining an item on anticipated income, which can be quite dangerous fiscally. The depreciation on such a thing as an amp is enormous, so making payments on it is not advantageous. Especially if you have the power of compounded interest working against you, payment plans are to be avoided, especially for non-necessities. 

I will never forget my father telling me, "Every dollar spent is a two dollar decision." (Every dollar spent is a dollar less that you have to invest.)

Even as a reviewer, I recommend no one needs to go into a payment plan for an audio component. The only exception might be on zero percent interest, and at a very modest amount relative to one's income, perhaps 1-2% of gross income. Even at that, you are turning potential opportunities against yourself by the opportunity cost associated with expending the money that could have been invested. 

I strongly recommend that under normal circumstances no one spend half of their income monthly on audio - for any component. Imo, In a balanced lifestyle the expenditure of audio should fall well below 10% of income, and as a percentage much below that after house payment. 

Frankly, the financial indicator that one is spending quite disproportionately on audio can be a "wake up call" that major changes are needed in life. Usually, where there is an extreme imbalance in finances, there can be imbalances in other areas of life. I am trying not to be judgmental of the OP in this regard, as I do not know all of the particulars. It is, however, shocking to consider any audiophile expending such an enormous percentage of income on gear. Maybe the OP's income is so terrifically high, and lifestyle so ascetic, that they can pull it off. We do have people with alternative lifestyle choices who live like misers daily in order to achieve extreme goals. Hopefully, that is at work here. But, still, it's an imbalanced fiscal lifestyle. Three years of saving would theoretically achieve a similar purpose, and without the associated risks. It seems there is little wiggle room now for the OP in consideration of the potential challenges that appear occasionally.  :(

In all sincerity, I hope the OP does not get financially buried by their own zeal for the finer things in life.  :(

It’s not that hard to pay cash for cars. One must be disciplined, and then typically buy at least 2-3 year old model. Some will even buy a more expensive import that way out of an effort to get superior longevity, i.e. Mercedes that could do 200 to 300K miles. millercarbon exhibits some characteristics of net worth millionaires. Denying extravagance and extreme fiscal personal policy is typical of them. Most do not have the knowledge or self discipline to prioritize that way. :)

Of course, such matters should be looked at holistically. It seems to be the smart thing to do paying cash for a car. Not necessarily the best option, however. One may get ahead by buying a new car at 0% loan APR, then investing the amount of the car over the period of the loan. Now the power of compound interest is working for you, not the automobile manufacturer. So, anotherbob is correct that some loans are actually advantageous; some marginally so, and others - when good fiscal discipline is employed - more so.

Of course, avoidance of buying any car is ideal, and one has to weigh the necessity of it. The person who buys used and drives it for 15+ years will do better than someone who flips cars and keeps making a payment, and very likely better than someone who buys new at 0% and invests. It would be pretty easy to run the simulations, and that is what a net worth millionaire would do. That’s how they get to become wealthy. They do not just guess or care less. :)