Hegel H30 or Bryston 7B3 monos

What specifically is the "magic" you lost with the Levinson pair, and what specifically are you looking to improve now?  Also, with all the wonderful amp options out there, why would you limit it to these two?

Thanks Jafant, I am VERY happy with the 512.  It is the piece I continue to build around.  The 436 are excellent as well, but they are getting a little older and I am curious if newer designs will have a better sound-same articulation, more depth, weightier dynamics.  The 436 are transparent to source and preamp and measure as good as most amps made today.  
I am curious about the power reserve in the Hegel 270 000uF capacitors vs 50 000uF in the 436.  It seems it could get a real nice grip on the 2 10" woofers in the Magico S5's sealed design.  Although, further research shows that when used as a monoblocks the H30 loses soundstage and width.  Not what I'm looking for.
The Bryston 7B3 measures as well as the Levinson 436 (http://www.avhub.com.au/product-reviews/hi-fi/bryston-14b179-power-amplifier-review-test-431015) but has more power- and a 20 year warranty. But how does it sound?  Haven't heard it yet.

Soix, I felt the Levinson gear had very good synergy.  I found the 512, 326s and 436 have excellent detail, and transparency, but ultimately lacked some soundstage, depth, drive and musical presentation.  I went with Vinnie Rossi's LIO as a preamp and recovered some tube warmth and 3d I was missing.  I changed speakers from Wilson W.P. 8 to Magico S5 (both excellent speakers).  But the S5 has a different sound, not as forward or hyper-real as the WP8s, so I am looking to add more of the slam and dynamics that I hear from the big rigs at the auto shows, while maintaining that transparency that is equally addicting.  
An amp that is similar to the 436 but with more power seems to be a logical step.  
Also-trying to keep all my gear black, cant do bright meters because of Home theater use, and probably staying ss for the amps. 

Keep me posted -firefightingrob

Happy Listening!

If you're looking for slam and dynamics without sacrificing transparency, I suspect you won't be disappointed with the Hegel on your Magicos. I'm extremely happy with mine in these areas with my Raidhos. I'm using one in stereo mode, which provides 675 watts into 4 ohms. Hegel doesn't specify the output into 4 ohms with the monos, but I'd guess it's considerably more powerful than the stereo unit (contact Hegel and ask them). Of the stereo unit, Pacula at 6 moons says: "I don’t believe there are loudspeakers beyond the Hegel’s power capacity starting with the Franco Serblin Ktêma through the German Physiks HRS 120 Carbon to the Ascendo System ZF3 S.E. and Avalons ending with the Sonus Faber Elipsa and Stradivari". And Harley at TAS says, "I also had the feeling that the H30 had virtually unlimited power reserves." My previous amp was more powerful on paper, but the Hegel is more dynamic and adds more control.

A couple reviewers (including TAS) thought the stereo amp sounded better than the monos--I suppose that's up for debate. Schneider at Soundstage thought the depth was lacking a bit, but that was in comparison to the Luxman which excels there--but then again, Harley says, "the palpability of timbres and images toward the back of the soundstage was phenomenal." I guess everything is relative to what you're comparing to, but I haven't noticed any deficits in stage width or depth. On the contrary, I find the soundstage and image specificity seem generous and accurate.

I use a tube preamp, as you're planning to do, which I think is a good idea. Overall, the Hegel is the best amp I've heard in my system, doing a fabulous job balancing clarity and detail with ease and liquidity. I haven't heard the Bryston, so can't comment on the comparison.