The only Hafler amp to meet your specs will be the XL-600. These were the last amps that were designed with David Hafler at the helm of the company and were manufactured from around 1988 - 1990 just before the Rockford buy out of Hafler and the later Jim Strickland Transnova amps came out. My XL-600 is mostly stock, I recapped the driver boards and made some resistor upgrades and replaced the bias pots. It puts out >550wpc into 4ohms @ 0.1% THD+N with both channels driven. My measurements of it are attached. It is one of the few amps that you'll find that the manufacturer actually gave a power rating into a 1 ohm load in the owners manual. The Excelinear amps are very reliable and have a delayed on & speaker protection relay built in. They use a thermostatically controlled fan which is both a positive and a negative. A positive due to the high amount of thermal dissipation it allows and a negative due to the noise the fan can add. I do find the fan noise on mine to be quite acceptable and only really noticeable between songs when its driving a hard load. A nice one can be had for $800 - $1000 and they'll only need minimal work done to them, usually a recap of the main driver boards, replace the bias pots, power up and adjust the bias and you're good to go, maybe two hours of labor. If you really want to go all out you could replace the 4 main filter capacitors too which would cost you about $150.
As far as the other amps go, the only other one I have experience with is the PL-700b which is 10+ years older than the XL-600. It puts out a massive amount of power. I rebuilt one for a friend about 4 years ago. I used some of the white oak parts but decided to rebuild the original driver board and modify the circuit using the tips that Steve Mantz of ZED audio had given on DIYAUDIO as well as user THD+N on the same forum. I rebuilt the amp with a full complimentary output stage and made changes to make it more stable. The amp's distortion dropped after the rebuild by a full order of magnitude and I didn't have a large enough dummy load at the time to test it to full power. But you can be certain it exceeds the Hafler XL-600's output. The one thing I do remember about the PL-700 is the heatsinks. They were undersized for the task and running inefficient speakers at high volumes seemed to get them hot in a hurry. They could have used a fan for sure. The PL-700 fully rebuilt will set you back a pretty penny. Even the units in need of a full rebuild are fetching very high $$$ now and if you go for the full WO rebuild this will cost you probably another $1k.
These two amps are quite different, the Hafler uses lateral mosfets in the output stage and the Phase Linear uses Bi-polar transistors. Some folks prefer the sound of one over the other.
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