If your whole system costs $40,000....


how much will you invest in CD player with that sum?

I have been wondering my CD section is the weakest link, its around 10% of my system cost. I wonder people who are using some $10k players how much their whole system costs roughly...... Anyone can share their experience in upgrading their CD players?
grandetech
In my case it is about 5%, (a Resolution Audio Opus 21, in case you're wondering).

However, you failed to tell us if this CD player is going to be your primary or secondary source, (or your sole source). If primary, you should probably spend a higher percentage. If secondary, then, (obviously), you should spend less than on your primary source.

(FYI: My primary source, my turntable/tonearm/cartridge, costs about 11% of my total costs.)

My two cents worth.
I'd estimate my main system (digital source included only) cost about 15-17K retail.

The cost to me was about 8-9K.

My main digital source is computer music server, DAC, + Squeezebox Touch, total cost ~ 1.6K with main and backup disk storage.

That's about 10% of total retail cost.
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I see you just don't get it. Trying to peg a percentage to a component is an exercise in futility. As far as retail my system is probably 60% speaker, 15% amp. 15% turntable/cartridge, and 10% digital source/preamp. How did that help you?

I was trying to answer what you initially posted and the only way to even begin to help is if we know what you have ....

I have been wondering my CD section is the weakest link,.

good luck
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Excluding speaker cables, ICs, and power conditioners et al, I have three systems that meet your criteria. For the CDP in each, the cost percentages are 8.2 %, 11.4 %, and 22.1 %. Figures are based on retail costs for new gear and what I actually paid for vintage gear. The CDPs were all purchased new; two of them are current models.
Survey:

"how much will you invest in CD player with that sum?"

Answer:

As much as it takes so that I enjoy listening to the music thru it. It so happens that at this time, it's around 10%.

I would consider it foolish to limit myself to a certain % of say, at or about xx%. I once put an extra system together a few yrs ago that paired a $900 2a3 SET integrated with a pair of %550 single driver speakers. Those are "msrp" prices, not street or used. The CD player was $3000. That works out to 200%. I really enjoyed it. I doubt I would have with a $150 (10%) player.