iPod directly into amp

What you need is an integrated amplifier/receiver and a decent iPod dock so you can bypass the headphone circuit in the iPod. Onkyo makes a decent dock, and I'm sure there are others out there... which would set you back maybe a $100 at the most. With $500 your options for an integrated with enough clean power to drive the Grand Pianos are limited, I second the Nad suggestion, but you might also look at Creek (there is one A50 on Audiogon right now) which would give you a bit cleaner sound. I recommend doing some research yourself in the archieves here and on other audio sites.
Good luck

I say do NOT use the headphone output of the ipod- it is already amplified to drive headphones - re-amplifying it just ain't right. Will be distorted - not enough signal strength - you'll have to crank everything WAY up (as scpetscott alluded to). Use the LINE OUT on the ipod via the dockport/30 pin connector. Use an apple dock or specially designed connector to get at the line out signal - then run it into a proper preamp or integrated amp with volume control. Another bonus to doing it my way is that you can run the ipod set to volume = zero. Battery will go a LOT longer because the ipod is not doing any amplifying. Just treat the ipod like any other source component - you need a preamplification to switch between sources and do volume control. But use the LINE OUT signal.

Thank you all for the feedback. So, the concensus seems to be integrated amp.

I do in fact own a docking station from Apple, so line out wouldn't cut into my budget.

I'll join the chorus here and recommend a dock for the iPod going to a good quality integrated. I've used that setup with both Creek and Audio Refinement Complete integrateds and been very happy with both.

You can get good information about docks by going to http://www.ilounge.com/index.php/accessories/.

The one I bought worked well. It has a line-out connection, charges the iPod and has a nice little remote for changing songs. It's this one from Kensington.

You'll definitely want a dock for your iPod that goes into the amp. This is the one that I currently use, but at an amazing price that I just saw on a deal site:

http://www.onsale.com/shop/detail~dpno~564547~descr~Kensington-Stereo+Dock+for+iPod.aspx

It works amazing, doesn't use the headphone jack, and has a remote. The only tricky thing is that when you first plug it in you have to use the remote (not the ipod or the amp) to turn the volume all the up for the the output of the dock.

If your music is encoded at a high enough bitrate, you will enjoy this immensely.