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

I'm wondering what resellers you find reputable for your purchasing. I've made three purchases with (The Music Room) in Colorado and they've been great. They guarantee their items work, have a 14 day trial period, and an easy to navigate website.

What other sites do you know of like this — not just that connect sellers and buyers, but that take in used gear, test it, rate its cosmetic condition, and offer a trial period? (I'm a bit wary of buying, say, an amplifier of $2k only to find it's not what it's supposed to be.)

This could be a general site, like The Music Room, or just a store that does this (good selection, prices, trustworthy, and trial period). Thoughts?

I agree, thus far I've had very good customer service provided by the Music Room.
Many Brick n Mortar (retailers) take in trades ...
This does not mean that any will check function and even offer any returns.
Many in Retail get to know their customers though.
Used is not as convenient as New!
Second (third?) TMR....if they don't have what you are looking for, contact them since they may be a good resource to find what you want.
I've also had a very good experience with TMR. Very responsive and fair to deal with.
Saturday Audio Exchange, Saturday Audio - Chicago audio store with new & used hi-fi equipment for music lovers Music Direct, I recently purchased a Musical Fidelity NuVista Vinyl Phono Preamplifier from them, I tried it in my system and it just didn't sound right so I called them and took it back, no questions asked full refund.

+1 TMR. Could not give them higher marks really. I've purchased 3 major items from them and their customer service is top notch. These guys are in Portland, Oregon and they are great.  Always new great stuff.
I have used tmr and music direct. Music direct is new gear but they offer trial period and no questions returns, just pay shipping on return. 
Like many others (including hifihandyman above), I've had good experiences dealing with Echo Audio in Portland, OR.
On a *very* tight budget and all of my purchases have been with TMR.  Honestly amazed at the system I have been able to put together.
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.
TMR, Hawthorne in Seattle, Audio Classics in Vestal NY and Gig Harbor Audio are my used gear go to to buy and sell
Great -- thanks for those. Some list their policies about try-out, returns, shipping; others don't. A phone call could take care of that, I'm sure.
Hawthorne and Gig Harbor Audio are also great, I've bought a number of things from both.
I second what @rego said: Reno HiFi gave me very good service when I tried out a Pass X250.8 a year or two ago. Really great people.