I second rok2id4's suggestion about tracking down some good string recordings. But before you replace any equipment as so many have suggested, try the Schiit Loki:
https://www.schiit.com/products/loki
Only $149, with a 15 day free trial and full refund minus only a 15% restock fee. So if it doesn't help with your problem, you are out only $22 - way cheaper than replacing a preamp, cd player, cables, or getting a power conditioner. Doesn't work and you are out $22, you can then then proceed to spend way more on one of the suggested fixes that also may or may not work. Regarding your speakers, I was a long time owners of the BC-1, for which I believe your speakers are the 4th generation replacement. While I've not heard the SP1/2e, based on how wonderful the BC-1s sounded, I would really hesitate replacing the SPs.
Only $149, with a 15 day free trial and full refund minus only a 15% restock fee. So if it doesn't help with your problem, you are out only $22 - way cheaper than replacing a preamp, cd player, cables, or getting a power conditioner. Doesn't work and you are out $22, you can then then proceed to spend way more on one of the suggested fixes that also may or may not work. Regarding your speakers, I was a long time owners of the BC-1, for which I believe your speakers are the 4th generation replacement. While I've not heard the SP1/2e, based on how wonderful the BC-1s sounded, I would really hesitate replacing the SPs.