Best Integrated 50wpc under 600 used

You don't hear much about Densen, but I have been extremely pleased with the performance of my Densen Beat Series B-100. A VERY nice sounding amp, and one which you hear very little about. It retails for around 1200-1300, but since they are somewhat unknown in the U.S., they tend to be difficult to re-sell and should be found used in your pricerange. I also own a Rega Mira which is a solid little beast (though not nearly as lucid as my Densen) that could probably be found used in your price range. Good luck.

Subdoofus,
Check out the charity auctions right here. There is an ASL (Antique Sound Labs) 5W/15W SET integrated - retails at $600, bids around $400 right now. Should be a great match. Or try one of the Bottlehead pre's with the ASL WAV-8's. You might also be happy with the Outlaw 1050 - and be ready for HT even if you don't want to set it up right now. Good luck!
Tim

Cambridge Audio makes good stuff--better than NAD. A sleeper brand, but prices for their stuff are reasonable. Try www.spearitsound.com for more info (no association).

Look at Roksan, Audio Analogue and Audio Refinement used.

I don't believe there is a "best." There are a few well built solid state integrated amps in that price range and they will vary more in power rating and features than in sound, (to me.) I own and have enjoyed 3 of them: Creek 4330R, Audio Refinement Complete, and Creek 5350SE. The 5350SE is beyond the price range. The ARC by YBA is wonderful as well and will be just barely at your price, used, if you are lucky. (I paid $850 for a demo.) The Creek 4330R is remote controlled, has a pre-out if you want to add a subwoofer later, and is much more powerful than its 35W rating. I have never heard the 4340. Look at the 4330. Save some dough and buy some more music. Study hard. Charlie