Advice on trustworthy audio resellers who check condition, offer trial period?

Upscale Audio sells used on their site.  I have only bought new from them in past years, but their service and support was good for me. 

I just purchased an SP-6 preamp from Echo Audio in Portland.  The protection circuit failed and my local shop repaired it. 

I sent a copy of the invoice and a pic of the 7 replaced parts to Echo and my card was credited for the entire repair right away.

Excellent attitude and great service.  The pre-amp sounds wonderful on my Maggies, replacing a Luxman CL-32 that finally failed after 40+ years (channel gain imbalance that is evidently not able to be fixed by Luxman).

@richopp Thanks for that tidbit. I'd add this: I ordered some Sennheiser headphones from TMR as a gift. The case has some discoloration on it and I asked for some compensation; without argument, they credited me $10. No argument, just did it. I know that's not a big deal, but the lack of debate/agitation about even small things does a lot to keep me sweet on a retailer.

Echo is the best place I've found.  More than once Kurt has talked me out of buying things because they might have only been a sideways move from the component I was considering replacing, not a good fit with my other components, etc.  

I have had a couple of instances where there were issues, one when a used cartridge arrived with no diamond on the stylus, they gave me a full refund and another where a vintage automatic turntable wasn't returning correctly, they fixed it right away and I still have it and it works perfectly. 

It's such a great place, that I almost hate to mention it because I often see things show up on their website that I want and someone else has already snatched it up.  Their prices are close to unbeatable.

TMR is great too, I've had good experiences with them, including when I purchased a preamp that showed up with some broken capacitors.  They paid to have it returned and repaired it quickly.

Anyone have experience with Kahl Audio? https://kahlaudio.com/about-us/philosophy/