You should definitely include the Adcom GFP-750 to your list. It retails for $1250 and can usually be bought on this site for around $800. This preamp is very neutral, and is "Class A" rated by Sterepiles, and has received uniformly excellent reviews from a number of audio review mags. The reputation is well deserved.
Preamp new/used under $900
Hey...I have a Rotel 971, NAD 314 (used as a pre), Classe Audio Seventy, and a pair of Hales Rev. twos. I don't want a pre that is warm, soft or laidback sounding. I would like the system to stay neutral erring on the side of cool. A pre that can help resolve very dense/processed electric guitar like Ministry would be super cool. Right now the dense music sounds a little mushy. right now im dense and little mushy too. A big soundstage is also a priority, but im not sure if preamps in this price range will vary much in that respect. Thanx ..im tired and hope at least half of the sentences make sense.