Nice looking build! I don't remember my Crack/SB ever having a blurry presentation. I built the amp back in 2014 and the Dayton caps were cheaper back then. I don't like going overboard with these type of upgrades. I don't believe the caps were a big upgrade but they certainly didn't degrade the sound and I am very happy with the amp's performance. Always fun to see if improvements can be made especially when it's cheap to do so.
I used insulated solder turrets for mounting the caps (see attached photo). If you look at my photo from the last post, You'll see where I drilled four holes for the 4 turrets. Then countersunk the holes in the plate for a flush screw mount. The Dayton cap wire gauge is plenty stout enough to be self supporting so they just hang freely from the turrets. Found these similar ones on e bay .... look for ....
M55155/209J01 MIL Insulated Solder Turret Terminal Lug Stud 4-40 Threaded 1/4"Hx
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Been using it this way for 7+ years with no issues at all.
You may want to ask Paul at the BH forum about the issue you are experiencing. I use Beyer DT-1990 Pro and they work great with the amp. Transport DSF files to an E50 and into the amp. Crystal clean rich sound with black background. The HD-6XX sound good with it too but ever slightly more veiled for my taste. Being older I like the brighter phones tor my natural lack of high frequency hearing.
Anyway, I wouldn't bother with high priced caps. I only upgraded the output caps and the volume pot, maybe $60 total. No further upgrades will be made. Good luck!