Is the Adcom GFP-750 really that good ?

I have owned both [several times].
The Parasound P/LD-2000 is overall sonically superior to the Adcom GFP-750.
I own a pair of Parasound Halo JC-1 monoblock amps, and the P/LD-2000 matches up extremely well with them.
Don't get me wrong, the Adcom is a great preamp. It is a bargain for what it does, especially used.
It is very transparent, dynamic, and detailed, and has excellent bass.
But: As Plato said, it is alittle dry and thin, has a somewhat recessed lower midrange, alittle etched and grainy on top, lacks ultimate top-end air and decay, and is somewhat dark sounding on vocals, especially in the Active Mode. It sounds sort of "HI-FI", if you catch my drift! It is alittle better in Passive Mode, but still has the same basic sonic signature. It is probably a good Class B preamp if it were rated similar to Stereophiles rankings. I do not feel that it is a Class A preamp. It does match up extremely well with the Adcom GFA-5802 power amp. Great as a matter of fact!
The Parasound P/LD-2000 is an underrated preamp! I love mine.
It is extremely detailed, extended at both frequency extremes, full-bodied, spacious, and gives true palpability to vocals and instruments.
I used to also own a Pass Labs X-2.5 and a Pass X-1, which I liked very much, but, in the end, I keep going back to the P/LD-2000. It has a certain musical "rightness" that the others lack in my system.
Results may vary in other systems and with musical tastes and priorities that differ from mine.
To each his own.

I agree with other respondants who opine that the GFP-750 is an exceptional value when purchased used. I recently replaced my GFP-750 with the new "Gain Cell" preamp from PS Audio. The new preamp is still breaking in, so I reserve final judgement, but I can confidently state that it is more resolving than the GFP-750. First impressions include a lower noise floor and higher resolution of detail, as well as greater dynamic contrast and speed, the latter particularly noticable in the bass region.
The only amplifier that I have paired with either preamp is the PS Audio HCA-2. The GFP-750 works very well with the HCA-2 in passive mode, using either single ended or balanced interconnects. Resolution is exceptional and dynamics are surprisingly good. Avoid SE cables, however, if you intend to use the GFP-750 in active mode with a very transparent amp like the HCA-2. With SE cables in active mode I consistently found the sound to be veiled, and fatiguing with extended listening, in comparison to the passive mode. Upgrade to a good set of balanced cables, however, and the active mode sounds just as transparent and sweet as the passive mode, with a touch more heft in the bass region. I enthusiastically recommend Synergistic Research Kalaidoscope Phase II cables (balanced) as an excellent choice for anyone interested in pairing the Adcom GFP-750 preamp with a PS Audio HCA-2 amplifier.

I would tend to agree with Plato and Daltonlanny on the sound of the 750. I had a $200 passive Creek OBH-12 that was awesome sounding! It even had a remote. I would have kept it except there were only two inputs. I liked it so much I thought passives were the way to go, so I picked up the Adcom. It was disappointing in my system. Sounded much like the two above discribed. The Odyssey Tempest is outstanding and took my system to the next level.