Arc preamp advice

Thinking of replacing arc preamp ls26 with  arc ref 3 or 5, 5se or ls28. Amp is arc ref150. Speakers are  proac d38. Based on everything I have read it looks like 5se or ls28 are the best options however I really don't want to spend 7/8k. Current set up sounds very musical so it's hard to envision how much better it could be.  Ideally  I would have listened to these to understand differences but that's not an option.  This will likely be my last major upgrade before I retire so looking for opinions. 

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