Sunfire Standard or Signature Edition

They both look like Standard 300-2 models, 5amp fuse and captive power cord.

I’ll check my archives.

The top one appears to be a 1st version Sunfire 300 w/ gold posts, captive power cord (no IEC), no power switch... bottom looks like the later model 300x2 w/ plastic posts, captive power cord, no power switch. Standard models operate at 390 joules (same as photos). These are not Signature Editions.
These are the Sunfire models...

1). Sunfire 300 Load Invariant   1996 -2000 (no switch)
    Sunfire 300 x 2 ... (end of Series 1) IEC, plastic posts.

2). Sunfire Series II 2001 - 03 325w/8, 650w/4
    Architect’s Choice (with on/off)       17” wide

3). Sunfire 300 -Two   2004 300w   19” wide
    - plastic binding posts, diff rear panel L/R layout
    - Balanced design**

Sunfire 600         1997 1200w/4 ohms   19” wide
Sunfire 600-Two   2004

Sunfire Signature     600w   1997   19”wide   $2995
Sunfire Signature II   650w     2001   17” wide
(uses gold spkr terminals).

The Tell-tale sign... model 300 operates at about 390 joules, 600 signature about 470 joules.

Also, back of Sunfire Signature 600
https://www.ukaudiomart.com/details/649279940-sunfire-signature-600-ii-one-of-the-most-powerful-ampl...

https://forum.audiogon.com/discussions/sunfire-signature-what-is-this

Thanks LowRider57. Good information. I saw the second post you referenced before I started this thread, and I was still confused. Both of my amps have the 19" chassis, and both have the captive power cords. I noticed that in the Series II manual, both the Standard and Signature show IEC connections, and I couldn't find a manual prior to Series II. So I guess I don't have a manual for my amps. Oh well, I bought them right and will likely bridge them and used them both for my B&W 802D's or Martin Logan Odysseys. Those speakers like a lot of power and it sounds like the current source might help them breathe. Then I'm going to sell either my McIntosh MC452, or my Mark Levinson 332 after George Meyer unbricks it. 

Yeah, that’s the same manual that I used. Bridging and bi-amping them is the way to go. I used one amp rated at 300wpc, 600w into my 4 ohm speakers... sounded terrific in my 12’ x 16’ room. Non-fatiguing, wide and deep 3D soundstaging, and a powerful low-end.

A little known fact; these first generation Sunfire’s are not fully-balanced. XLR input is shorted to single-ended. Will you be using balanced cables? This will prevent any ground-loops and provide a lower noise-floor.

Here are specs for these amps...
Sunfire 300 Power Amplifier - Class AB:
- 300 watts/ch into 8 Ohms, 600 watts/ch into 4 Ohms
- frequency response 1 Hz - 80 kHz, balanced and unbalanced inputs
- input impedance 42 kOhm
- Input sensitivity of 1.64V for rated power (300W)
- output impedance 0.01 Ohm (voltage source),
1 Ohm (current source)
- Output voltage (@ 8W) is 48.9V
- Damping factor 150

2nd generation 300-2 is fully-balanced....
- Input sensitivity for rated output:
Unbalanced: 1.64 Vrms,
Balanced: 0.82 Vrms
- XLR Input impedance:
10 kΩ, each leg balanced to ground Female XLR
Pin 1 is ground Pin 2 is positive (hot) Pin 3 is negative (cold)

Notice the difference in input sensitivities.