I am in the market for a $ 5-6 k monoblock amplif

+3 on the Rogue Audios especially, if you're looking for a tube sound.  Fantastic sound in that price range, you need to really take a listen.  If you're looking for a SS amp, I would put the Parasound JC1 and Hegel H20 on your list.  

I suggest you look at the Hypex Ncore NC400 Bridged Monoblock CLASS D Power Amplifiers.  The cost for this model is $2,980 plus shipping. 

I purchased the Hypex NCore Class D amps from James Romeyn Music and Audio, LLC (James). He was very helpful answering my many questions and I suggest you contact him for more information on his assembled Hypex amplifiers (he offers 3 models). Please see:

http://jamesromeyn.com/old-pages/home-audio-gear/hypex-ncore-nc400-build-service-on-time-or-free-bui...

Choose from Three Hypex Amplifiers

1. Stereo powered by Hypex SMPS1200A400, 600W @ 2 Ohm, 1 Ohm minimum, $1,490/each, 1200W Hypex power supply for 600Wpc, dimensions 2.8″ x 9.8″ x 12″ (70 x 250 x 308mm), 8.5 lbs (3.9 Kg), specify face plate finish: black or natural aluminum. 

2. Bridged Mono Bloc powered by SMPS1200A400, 1200W @ 2 Ohms, 1 Ohm minimum, $2,980/pair, 1200W Hypex power supply, dimensions 2.8″ x 9.8″ x 12″ (70 x 250 x 308mm), 8.5 lbs (3.9 Kg), specify face plate finish: black or natural aluminum.  I own this model.

3. Regular Mono Block powered by Hypex SMPS600, $1,900/pair, 600W power supply, specify faceplate finish: plain black, black with NCore logo, plain natural aluminum.

This is my first class D power amplifier and, based on my results, sounds terrific.  I am thrilled with how good my system sounds.  I am hearing details, imaging and bass that I have not heard before.  Of course, everyone has a different opinion on this subject.  You never know “how it really sounds”, until you listen in your room and audio system.

NOTES:   I am using the Bricasti volume control and do not have a pre-amplifer in my system.  We adjusted the Hypex NCore NC400 mono-block power amplifiers so that it accepts a higher incoming signal meaning I can move my Bricasti M1 SE DAC volume control closer to zero.  After conversations with Bricasti, Hypex and James (James Romeyn Music and Audio, LLC), we decided to remove the R141 (circuit) from my Hypex NCore NC400 bridged mono blocks, thus lowering gain by 14 dB, requiring 14 dB higher M1 volume setting for same playback level.  This is more complicated than I expected but it solves the problem.  When you connect the Bricasti M1 DAC to a power amplifier, you have to balance the M1 DAC to the power amplifier in order to achieve your M1 volume settings CLOSE to 0db.   

Class D is a good choice, look at Merrill Audio and do a search on their THOR monoblocks, can't go wrong IMHO.

I absolutely love my Bel Canto ref 500Ms. I have had them for four years or so, having graduated from powerful older solid state amps (b&k and adcom) .  I've always been happier with more, rather than less power.  Anyway, the class d bel cantos are wonderful--warm and musical and I haven't grown tired of them at all.  In your price range, the newer Ref 600Ms are supposed to be even better.  Red the reviews.

best of luck,
tom

The OP posted in 2011, so it's unlikely they are still looking for an amp... BUT, I will second the recommendation for Merrill Audio.  I picked up a pair of Thor mono's and was completely blown away when I first heard them.  While these are my first class d amps, I've owned amps of various topologies in the past - atma-sphere, vac, pass labs, McIntosh, Levinson, etc, etc - and feel that the Merrill amps are not 'great for class d' they are simply great amps period.  Very highly recommended.