Best Integrated Amp (for me)

I have Kef R300s a very similar speaker to the LS50s. I chose them after listening to both side by side for hours. The R300 had better bass and was more aesthetically pleasing to my SO.  I drive mine with Marantz PM8005 now the 8006 for the last 5 years quite effectively and with very music results. You can get one for $1000 from many dealers. It is made in the Marantz Japan Reference factory and comes with a 3 year warranty and very conservative power ratings. It is a Class AB and has a slightly warmish sound. You can bypass the preamp and listen direct to the power amp which I do very often on good recordings. It also has excellent tone controls for not so good ones. I also really like the Rega Brio which is a bit smller and simpler but can also be found for a grand and has excellent sound. 

I ended up getting a Marantz 140 amp on ebay for $800. Now I'm going to start looking for a decent but not-super-expensive pre-amp to accompany it (until I can save up more $ to get myself something better... maybe the Marantz 3200?). If anyone can recommend any inexpensive pre-amps, I'd be curious to hear!

Mine,

Take a look at Peachtree Audio.  They have a reputation for good products, reasonable  prices, and some of their amps have wood finishes, giving a vintage look.  

In your price range most of the stuff mentioned here is pretty boring.

I'd just go for the little Rega which has some actual life to it and be done.