Accuphase E5000 vs Gryphon Diablo 300

At this price level you have a lot of very good options. Gryphon, Accuphase, Vitus, Boulder, Pass, T+A, Manley, Line Magnetic, BAT, just to name a few.
 

Given youre talking ‘end game’, the most important thing (in my opinion) for long term satisfaction is to concentrate on the emotional response you get from listening to a particular amp, as part of your system as a whole. Try to ignore price and measured performance (and reviewer descriptions) as these do not correlate with your own personal enjoyment of a piece of gear. If you really want this to be your last amp purchase, then I think you are more likely to be able to step off the upgrade merry-go-round if you demo widely with different topologies (tubes, SS, Class A, A/B, D, hybrid) and ultimately follow your gut (heart) rather than your ear. By this I mean pay attention to how you feel when you’re listening, rather than the level of detail being excavated from a recording, or size of soundstage being drawn. 

Good luck and enjoy the journey. 
 

Boulder 866.  It's crazy good with a top US company to back their products. 

As a Gryphon Diablo 300 owner, I would DEFINITELY go with the Gryphon. I auditioned quite a few amps before landing on this one. It simply doesn't have any weaknesses!

Accuphase can rock. 

Auditioned both and went for the Gryphon, mainly because it's sound "architecture" is bass-dominant, so given your music tastes I'd go for the Gryphon. Another thing is price, the US Accuphase distributor is greedy so you'll be paying more than you should. Another option you might not hear about much on AGON is T+A from Germany, they make great integrateds, can't remember the top model, but you might find it hard to demo unless you live in a big city.

I would also suggest listening to the Moon 700i v2.

Accuphase not for Rock. 

My room is:

26 x 14 x 8
 

I did think about adding the Ayre AX-5 Twenty to the demo list too. But I heard it was a bit light on for bass / dynamics.

you should listen to the burmester 032, best i have heard

Just grabbed an Accuphase e280, $6700, ouch. Did not need it really, but what the hey....was told it was last one in US, with over 3 month wait for next shipment. Privacy increased from $5999 (by $700 bucks, crazy!) , but crazy I am I guess.  So I’ll have this and my Clsss A Sugden, I think I’m good for a long time. Never heard of Gryphon...so can’t be of much help.

op

given your two choices posed, and given your stated music preferences, as excellent as the accuphase gear is, i would choose the gryphon

@rfc, how big is your room and how loud do you listen?

Unless you are filling a very big room or play your music at concert levels, you might not need so much power with the Spendors.   I've got D9s and in a 12x17 room and driving them with a Pass X250.8 I never once it had it leave its ~18w Class A bias playing in the mid 80 dBC range.   I then switched to the XA30.8 and could play it in the mid 90 dBC range without it leaving its 30w Class A bias.

You might be able to save some $$ unless you specifically want a high powered amp...;  one of the many virtues of the D series I really like is it doesn't require an uber-amplifier to make it boogie or sound good.

Both great amps and really hard to see going wrong with either, and great speakers as well BTW.  If I was looking I’d add Vitus Audio to your list.  Best of luck. 

Both are excellent amplifiers and so is the d"agostino momentum.

I listen to classical, as well as blues & jazz, so I would opt for the Gryphon. YMMV, so audition them first.

You won't go wrong with any of them