IMHO and with my limited knowledge/experience. I believe you are going to need two amps. I currently have a fostex TH-600 (which I would think has similar power requirements as the D5000) and a HE-400I (which I think is a little harder to drive then the s) and I use an Audio-GD NFB11. I also have the LCD-2's on the way but I'm pretty confident the NFB11 doesn't have anywhere near the power needed to properly drive those headphones. I'm currently looking at the NFB-1amp or the LYR2 for the LCD's still not sure if I want to go SS or Tube or both. The NFB-11 is $325 plus shipping.
He would not need 2 separate amps. Deckard has 3 gain settings and should be able to power everything he owns and the huge majority of headphones on the market, except maybe a few weird ones. It has plenty of power.
Also - the LCD-2 really is not that hard to drive. Most decent amps should do fine.
I can also plug it straight into my Macbook with a 3.5 mm adaptor and it still sounds great. They really aren't as picky as people seem to think.