Best Integrated 50wpc under 600 used

Subdoofus, you have several good choices in this price range, which I have listed in my order of preference.

Musical Fidelity A3 int. amp 85wpc ($1495 new)
Audio Analogue Puccini SE 50wpc ($995 new)
Creek 5350 75wpc ($? new)

These are all very clean sounding and very musical integrated amplifies that would sound particularly good with high efficiency speakers. You should be able to pick one up used for ~ $600. Check Audiogon, Audio Shopper, Audio Web, and area stores for used/demo equipment.

If you are willing to spend a little more, consider the Creek 5350SE. A bit more power and more refined.

If you would like to spend less than 1/2 for a great little amplifier, I have an Arcam 6 35wpc that I am selling to upgrade to separates. I am currently using this British "giant killer" with modestly efficient Vandersteen 2ce signatures. The combination is both powerful and musical. The amp also has two pair of 5 way binding posts, so you can bi-wire speakers if desired. You can youu the difference to buy more CD's or books if you need them. Drop me an e-mail if you are interested. I was a starving grad student once myself, but that's no reason to give up good music.

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