Hafler XL600 Vs Hafler 9505 Much difference?

     I wouldn't use Schottkys in these amps either; especially since both rectifier bridges (L&R channels) are mounted on the front of the horseshoe shaped heatsink, very close to the outputs.    BUT: some people swear by them.

     I've used IXYS HiPreFRED and FREDs, in quite a few upgrades (my own and others'), with excellent result.

    Updated Parts Connexion, discrete rectifier/PCB (etc) info; in case there's further interest.

    That MUR860 bridge should be quite an improvement, in a lot of amps.

https://www.partsconnexion.com/cgi-bin/sc/productsearch.cgi?storeid=*20b7b4534d0a875b77f1157d6bb78322a865&search_field=rectifier

Mr C- You're welcome. Happy listening!

Chances are good that what you're hearing as a, "bass problem" with the 9505, is a case of expiring power supply filter caps. I've been using mine to power the bottom of my actively bi-amped system, for a number of years. My filter caps went south, about three years ago(symptoms appeared earlier, of course). The differences would be much more noticeable(across the board), if the amp was used full musical bandwidth. Especially given that you seem to enjoy cranking your tunes. These made a world of difference, but you have to leave the top off the amp, as they are slightly taller than stock: (http://www.digikey.com/product-detail/en/B41456B9229M/495-4228-ND/2269437)

Should have mentioned; those caps are slightly(10%) over the stock uF value, very low ESR and long life. You can further improve your 9505's presentation, with a pair of these(easy to install) FRED bridges: (http://datasheet.octopart.com/VBE17-06N07-IXYS-datasheet-143416.pdf), higher quality binding posts and RCA's, all of which can be gotten from Michael Percy: (http://www.percyaudio.com/Catalog.pdf)

I'm guessing you didn't check out the link that I provided.
(F)ast (R)ecovery (E)pitaxial (D)iode It's been my
experience, that their being substituted for common bridge
rectifiers, eliminates much grain/noise from gain circuits,
resulting in a more natural presentation. Regarding the
leaving off of the amp's top: I suppose it could be dangerous,
if there are those around that might place their hands in the
amp. I'm not faced with that issue. If I were; I would use
stand-offs(about 1/2") and longer screws to reattach the top.

Wish I knew someone competent, and close to you, that I could recommend. If you lived in Indiana; I'd help you myself. In reality; one only need be able to use a screwdriver, to replace the filter capacitors(in the 9505). No soldering involved. Just disassembly/reassembly. It's unfortunate that Rockford has stopped supporting the Hafler line, with replacment parts & service. Hope you get your tunes restored, and soon.

KUDOS! It's a good thing, to learn to do repairs on your own. Enjoy your tunes!

Mainly; a greater sense of dynamics, faster/more tuneful low-
end, less noise(some call it, "blacker background) and a
smoother/more detailed top end(not to say muted, recessed or
falsely accentuated in any way). They also allow upgraded
fuses and PCs to show off their benefits more obviously.
There are a few electronic manufacturers that offer them, as
an upgrade. ie:
(http://www.aebycary.com/shop/upgrades/hexfred-rectifiers/)
(http://www.rogueaudio.com/The_Magnum_Series.htm) Of course;
upgrading your filter caps adds to the improvement too.
Parts Connexion also offers these rectifier PCBs, so you can
more easily do a discrete HEXFRED or Schottky bridge:
(http://www.partsconnexion.com/kits_sub_assemblies.html)
(http://www.partsconnexion.com/rectifier_diode_cree.html)