Any reccomendations for amplifiers for my Quad 988

My system is:
PS Audio power plant
Cary 303/300 CD Player
SAS Audio 10A preamp
Quicksilver V4 Mono Blocks
Quad 988 speakers

I find the the sound gets congested when listening to large scale orchestras. No issues with vocals
I heard them sound very nice (superbly defined 3D images of instruments in there own space) with Conrad-Johnson amplification (in a store demo).
I am using vac 70/70,s with 989,s and they perform very well.Have you listened to both output taps?Are the Quicksilvers plugged into the power plant?I tried one of the latest ps plants and it helped the cd player but created congestion when either of my phono stages or line stage was plugged in and the power amps into the ultimate outlet was a disaster.Several people that have posted here are using amps with less power than yours with Quads and are happy,Mike Sanders has been building amps for a while why not e mail him.
I have been a quad owner for over 20 years and I now own the 988's.Even if I win the lottery today,Quads will always be the one and only reference for me.I have used many different tube amps,including single-ended and Otl's but I have found that the KARAN solid state electronics from Yugoslavia works best for me(tube sweetness,grain free,with lots of controll)and I dont have to worry about playing with tubes.Your Quicksilvers are good amps.I would get rid of the power-plant.I use the Sound Application line conditioner plugged into a 20 amp line or you could use the Shunyata Hydra.Keep in mind Quads dont play very very loud,and in a room thats not too big I dont hear any problems.I also use a pair of Rega Vulcan subwoofers with my Quads and I have my speakers mounted on Sound Anchor stands 12 inches off the floor.The sound really open up because the Quads are much more relaxed with the subs.Stay in touch.
The congestion you describe may be a function of several things: first, the Quads cannot really reproduce the 'scale' of a full orchestra at full swing with real conviction, dynamics and authority. Yes, they are beautifully coherent, and will produce bass if properly set up, but I have never found them to provide the deepest foundation that is essential to a convincing presentation of large scale music or the dynamic swings associated with it. (Mind you, my long, long experience is with a pair of Crosby Quad 63's that I have owned for decades, not the same as the 998's, but I suspect that there is not a huge difference). I don't think its a question of a bigger amplifier- the Quads seem to be very happy with smaller amps (I had great success in the day with an ARC Classic 60 and would suspect that Quicksilvers, Jadis, or other more 'modern' tube amps would give you almost all their performance).
THe other area where potential 'congestion' may lurk is in the front end- I have gone thru a serious set of upgrades in the last 4 months- from Well-Tempered TT and ARC SP-10 to Kuzma Reference and Triplanar to Kuzma XL and Airline, all using a high-end Lyra (Parnassus, now Titan i). The change is very dramatic- the Well Tempered is musical but frankly, a little 'light'; the change in phono stage to a Steelhead, and a more modern but still 'musical' line stage- Lamm 2- has brought the front end up to very authoritative standards.
Finally, I don't know how much all those improvements would have changed my own view of precisely the congestion you are complaining about, since I made the very dramatic change to a horn based system. In fact, I had some of the same complaints you did about image congestion, and having gone through what amounts to a complete change of system (I still have all the old equipment, including the Quads), I can tell you that the combination of serious front end plus horns makes this a non-issue. ( At least most of the time- there are recordings that are still far less big and open than others but i can now, with a decent recording, produce the scale, dynamics and authority that I couldn't reproduce with the Quad).
Your amplifier is fine with this type of speaker. My friend even uses the lower power Quickie Triodes with the 988 and it is sufficient as long as you don't ask the speaker to do things it wasn't meant to do. If you consistenly listen to orchestral music at a loud level this speaker will sound strained, its the nature of the beast. The 988s excellent detail and coherence is great for baroque, chamber, light jazz & vocals like you said.

I would look into custom horn designs.

Good Luck!*>)