Best speakers with Pass labs X-350.5

try wilson audio sophia 2

I think you'd enjoy the Wilson WP7 in your system.
With the ARC Ref2 and X350.5 I would not worry about hot treble with the Wilsons.
Dynaudio should be a good match as well.
I don't know what you meant by whisper treble on the 802Ds though. I think the X350.5 may be just about the starting point as far as power is concerned fot the 802D so if you don't listen to heavy metal at ear bleading levels, then it may do.

I found the Audio Physic speakers to be a great match with Pass Labs amplification. I had the X-1 pre with the X-350 and the XA-160s matched at different times with A.P. Virgo IIs and finally the A.P. Avanti IIIs. I chose the XA/Avanti III combo over the XA/W.P 7s.... to my ears a more natural presentation.

I agree with what Rost said regarding Dynaudio C4 and also Sonus Faber speakers. A friend of mine bought the X350.5 right after he heard mine in my system. He has a very similar setup as you, Audio Aero CD player + ARC Ref 2 Mk II + X350.5 and Dynaudio C4. I did not find the combo as musically involving as I like. It's a nice sounding system overall, but something is just missing. (It could be due to his room, because I heard the C4 driven by all Sim Audio products at the Stereophile show and liked it.) Another friend has a pair of Sonus Faber Amatis, I think pairing it with the X350.5 would be too much of a good thing making it sound too syrupy. (But some people like that)

I think all the comments above are valid. And I understand where you are coming from. I have an ARC LS-25 Mk I w/ GNSC ref mod and X350.5 driving a pair of Verity Parsifal Encore. I've been thinking of upgrading speakers for many years anf finally pulled the trigger a few weeks back. I only got permission from my "boss" to get the speakers and nothing else. For that matter, no upgrades were allowed for the next 5 years. So I wanted to make sure that the speaker-upgrade will not cause me to turn my entire system upside down. I've just received the Parsifal for about two weeks. The tweeters have just been upgraded by Verity so they are still breaking in, but I really like the sound.

Just my 2 cents. As others have stated, make sure you listen to the speakers you are considering. You would at least get an idea of how the speakers would sound in your system.

FrankC

I am using Eggleston Works Andra 2 speakers with my Pass Labs x350.5 Amp.
Previous to these I had the Von Schweikert SR 4 Mk2 and before that Legacy Focus speakers.
Each change was a major upgrade.
The Andra 2 have the cleanest bass notes I have heard.