In search of Audible Nirvana, on a budget.

I'm sure you meant GFA 555 and for under $1K new I would recommend either Aric Audio or Mapletree Audio. Both offer all tube design preamps that sound marvelous with older SS amps like the GFA 555 and alike.
I have paired the 555 with Aric's Unlimited preamp and it sounded great. Took the edge off the Adcom especially at higher volumes. I don't think for under $1K you can anything new or used that could beat either of these preamps. My personal opinion of course.

Several good choices here and on USAudiomart. There is a Music Reference RM5 mkII & mkIII available on both sites. I had the mkII for 5 years (many years ago), it was a great preamp. Mine was an early RM5 in silver upgraded to a mkII. I loved it. Very neutral sounding, 3 - 6dj8 tubes. Others I would consider are the cj PV5 or Counterpoint SA3. Moscode Minuet in A is also supposed to be an excellent preamp too. I have also heard very good things about the Mapletree preamps as well.

My Music Reference mated up extremely well with everything I put on it (B&K ST140, McIntosh MC225, B&K EX442, Paoli monoblocks, Music Ref RM9) except for the cj MV50, which it sounded out of phase and was looking for a PV5 at that time to mate up with the MV50. In looking for one of these older 80’s tube preamps, its good to note that they have been recapped and upgraded.  

An updated Dyna Pas preamp is also a real sleeper as well.  I would say the Dyna and cj preamps are probably more tubey sounding than the Music Reference.  Perhaps you could try 2 tube preamps - the Music Ref and a PV5 or Mapletree and see which one mates up better with the Adcom 555 amp.  You might prefer a more or less tubey sound with the Adcom 555.

Also note that the Freya allows 3 settings…passive, FET, and tube, so you can see what's what regarding the tube vs SS sound you like from the comfort of your listening seat. The tube setting is MUCH louder than the other two so surprises and hammering on the walls by neighbors can result from not adjusting the levels when switching around. I prefer the tube setting on this preamp, but I do switch it around to see if tube "coloring" is creeping in to harmonically grease the proceedings, but so far no problemo, and the only issue is compulsive spending on interesting 6SN7GTB tube options…chrome domes for days!

Check this Brown Audio Labs out!
http://www.theabsolutesound.com/articles/brown-audio-labs-sp-1b-preamplifier/