Need Help on HeadPhone AMP

Take a look at the Cayin unit. Great sound, great value, high resale value.

Another very good sounding headphone amp is the Mapletree Audio Designs, of which there are several variants. They are an especially synergistic match with the Grado RS-1's, but sound good with various Sennheisers and the AKG 701's in my experience.

Lloyd Peppard is coming out with a special edition (using tube rectification and EL-84 tubes, I believe), which is being issued this spring.

Again, you can get a variety of user experiences concerning this amp/phones at head-fi.org. But the amp/Grado combination is a screaming bargain and should not break $2000 combined.

Hope this helps!

I love my Headroom Desktop headphone amd & DAC with the AKG 701s. About as close to bliss as it comes in my book.

The Burson HA-160 headphone amp just got a rave reveiw from Srajan @6moons. It retails for $699 but partsconnection might have it for less.
As for headphones, it's all a matter of taste.

Your headphone selection will probably depend on what type you music you usually listen to. For classical and jazz I think the AKG K701/K702 is pretty hard to beat. They are known for their huge soundstage and great clarity. If you are more into rock than the Denon D5000's would be a great option. Many people have two sets of headphones (the above would cost less than a grand). Beyerdynamic DT880's are popular all-rounders along with the Sennheiser HD600/HD650's.

The woo-audio amps are great (take a look at the WA6SE) and so are the headamp, audio-gd (Phoenix or Rox), ray samuels, and headroom offerings. There are so many choices out there and the best option really depends on your headphones and personal preferences. I'd head over to headfi.org and go browse around their forums. You should be able to create an amazing sounding headphone setup for under $2500 along with your PS Audio DLIII.