TB. Looks like you already found the Steve Huff review of the 518 and 219. He's having such success driving your speakers with the LM amps. I haven't heard the 219, but have had similar experience with the 518's "fat" sound. With my Merlins, this is very welcome and I'm happy to have a bit more bass. Mind you, that isn't code for "bloated"-- it's taut and tuneful bass rather than one-note boom. Steve does seem to prefer the 219 with the Sonus Fabers, but I believe that amp is about $3k more than the 518 and those 300b tubes make for expensive tube rolling, especially considering how expensive 845s are.
Steve's experience should give you a lot of comfort. My dealer wouldn't let me bring the amp home either, and bringing my speakers into the shop was definitely a distant second choice, but I did get to spend as much time as I wanted driving my speakers with the 518 and was therefore absolutely sure it was the right choice. It's a bit more hassle, but you get to the same desired place. I also got the benefit of the store's expertise: without their suggestion and blessing I would never have thought/dared to change output taps on the fly to experiment and end up discovering the 16 ohm taps sounded best on 8 ohm nominal and 6.5 ohm minimum speakers.
