Amp recommendation for KEF LS50

I heard the LS50 with Primaluna integrated - I think the basic model, and they sounded fabulous. You could get the HP model within your budget.

this might sound like a dumb question, but I have never owned a tube amp..what do they do to the sound in comparison to solid state integrateds? (which is all I've ever owned)..Also, do tube amps only perform well with certain genres of music? I listen to a wide variety..

Mark Levinson 331 there is one on sale on Agon

I borrowed a Primaluna integrated (Prologue) from my local dealer recently and it sounded fantastic!  This was my first foray with tubes and I was impressed by the impact and large soundstage; nice, tight, deep bass too.  I've never heard the LS50's, but I can vouch for the Primaluna.  Another great amp in your price range is the SimAudio 250i. Occasionally, you'll see the Sim i-1 (original 250i) for about $800 on Agon.  I liked it so much I eventually bought their 700i.

Yamaha AS501 (2x85 watt) or AS701 (2x100 watt)? See here for reviews of the previous models, the AS 500 and the AS 700:
http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s500-amplifier-review-test-395710
http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s700-integrated-amplifier-393552
The added benefit of the new models is that they have digital inputs as well. The executive summary is that these are perfect amplifiers that behave impeccably, even under difficult loads. They will not add to or substract from the sound. Harbeth will use an AS701 at the upcoming Bristol audio show, to demonstrate their P3ESR. The argument is that you do not need expensive electronics for excellent sound.

I paired LS50s with a Creek Evolution 100a for my bedroom system and love how they sound together. Standard it comes with analog inputs only, but Creek has tuner, DAC/Tuner, & phono modules available that can easily be added to keep everything a 1 box solution if you need those functions. If you already have separate ones you like you or won’t need them, you aren’t paying for something superfluous. I talked to another audiogon member who has one and he noted it was better than his Peachtree Nova 300 with the Kefs. 

If you are interested in maximizing performance you may want to consider selling your ls50s and getting into a pair of ls50 wireless. Darko did a test and had to go way up market when pairing electronics with the passive ls50 to get them to outperform the active. 

I second robr45. Having owned both the wireless is vastly superior in every regard.

PeachTree Nova 150 is great with the LS50's. Better than my old combo of Benchmark DAC2 with Parasound A23 amp. I think the Parasound was the weakest link. The Benchmark DAC is better than the DAC in the Nova 150. Overall the Peachtree package is perfect with the LS50's. I actually made money by selling my old gear and buying a used Nova 150.
 
Darko has a review on PeachTree with the LS50.

Job 250 mono amps will kill on the LS50. Add a low gain preamp,it's heavenly.