down to earth amp for Avalon Eidolon

By down to earth I assume you mean reasonably priced -- which could mean used.
I remember the following amps sounded nice paired to an old pair of eidolons (i.e. not the diamond, etc). DO note that these are quick dated impressions, that I listen to classical mostly, and that I like dynamics.

A mid-range Spectral stereo amp -- should be reasonably priced used.
A top Symphonic Line integrated (now that's expensive new -- but possibly much cheaper used??)
A Plinius 250 (I think)
An ASR emitter (not the huge thing with the many PS, just one PS)
A pair of Manley monos (the Stingray in mono version) -- not very expensive AFAIK
A pair of Densen monos also a Densen stereo (~100/channel, don;t remember the model number)

There were other very expensive amps involved. Of course there's a plethora of other amps that I haven't listened to. This is just a listing of products I remember. Good luck!

Gregm, Driver, thank you for your input.

Anyone listen to Eidolons with ASL Hurricane, Gamut D200,YBA Passion 400 or Jadis Defy 7?

My friend owns Eidolon Vision with all ARC system(VT200MkII/REF2MkII/CD3MkII) and it is very good sounding.
You can find used ARC VT200MkII for $3K-$6K(depending on units age and condition) and it will drive your Eidolon's without any problems... If you want new amp then check Rogue Audio Zeus.

Since you mentioned the Gamut 200 -- I didn't like it (the previous model) with the Eidolons. It was one of the amps we played with.

On the contrary the Passion stereo was exquisite, outstanding. But seriously expensive, so I didn't mention it. While we're at it, the best sound (along with the YBA) was a Symphonic Line "Kraft" class A stereo. Ridiculously expensive.

Consider a used Atma-Sphere MA-1 MkII (140w OTL monoblocks). They sell on the used market for around $6,000. The higher powered MA-2 MkII.3 is what I use with my Eidolons, and the combination is outstanding in every way, but the cost of the MA-2 may push beyond what you consider "down to earth". Ralph Karsten says he has a number of customers using the MA-1 amps very successfully with Eidolons.