Have you had a look on head-fi?
Ok, amp wise, what features are you after? I'm guessing you'll probably want to use whatever portable amp you buy with your laptop/desktop right? Then what you'll want is a headphone amp/DAC combo which can connect to your PC via USB. Doing so bypasses the (often crap) internal soundcard and gives a much better signal.
Several options you could look at depending on what you want to spend:
1) Practical Devices XM5 -
http://www.practicaldevices.com/index.htm
2) Nuforce Icon Mobile -
http://www.nuforce-icon.com/Product-Icon-Mobile.htm
3) iBasso P3 -
http://www.ibasso.com/en/products/show.asp?ID=41
4) Meier Corda 3Move -
http://www.meier-audio.homepage.t-online.de/
I have no idea how much you want to spend, so I just quickly noted a few which I think are well worth the money. I have a Meier Corda XXS, which is basically the Corda 3Move without the DAC section, and it sounds fantastic with the Grado SR60. The practical devices XM5 is another one of my favorite portable units. Its well made, has op-amp rolling and buffer chip slots so you can fine tune the sound to your liking later on and can be slightly adjusted to suit whatever source you have it hooked up to.
The iBasso comes with a ton of extra accessories and is very good value. I had the previous D2 Boa, and that impressed me with its performance for the price.
The Nuforce is the cheapest one there, but that doesn't mean its rubbish. It does definitely sound worse than the others from my own testing experience, but certainly not a bad performer for the money and it is the most portable of the 4 options.
The thing with the SR60 is that it doesn't need an amp to sound great since its quiet easy to drive from most MP3 players, but getting an amp now isn't a bad idea since it'll be handy as you progress on with your audio journey.
If you don't need the DAC functionality, then you're open to even more options.
For example, here's my mini3 amp that I built:
It can be built for about $90USD if you're handy with a soldering iron.
If you decide you don't need a portable amplifier, however, I suggest this for home use:
http://cgi.ebay.com.au/ZERO-24-192-...ms=65:1|66:2|39:1|240:1318|301:1|293:1|294:50
I have one at the moment, and it sounds very good for the money. Mine has a few tweaks done to it, and the performance/price ratio is spot on.
Here's an extensive review of the Zero from head-fi:
http://www.head-fi.org/forums/f5/review-zero-24-bit-192khz-dac-headphone-amp-pre-amp-269458/
This is now my favorite portable combination:
Heavily tweaked iRiver H332, Meier Corda XXS amplifier and Sennheiser IE8 IEMs.