I'm looking at buying a Sennheiser HD 598, but want to get it with the amplifier.
Any recommendations? Any tips would be appreciated. Mainly looking for affordability and reliability.
I'd recommend the usual suspects. Schiit Magni or Vali (I use Vali with my 598) or Objective2 is probably where you should start. This is the $100-$150 range, and I personally wouldn't go too far beyond this for 598. Amps are great, but you get the most bang from your buck from headphone upgrades. I personally am not too fond of any amps cheaper then these, but Bravo Audio v2 or FiiO E07k are defintely worth mentioning.
Or, if you really want an affordable option, the Asus Xonar DG (has amp built in) is probably enough for the 598 and only cost $30. It would be the minimum I'd pair a nice headphone like the 598 with.
Do you need it for mobile use as well? The Schiit and O2 is so much over kill for the 598s a cheap cmoy amp will be more than enough to drive them.
I'd recommend this : http://www.jdslabs.com/products/1/cmoybb-v2-03-headphone-amplifier/
or an e7/e07k would also do fine plus it has a built in dac.
I didn't know people used the 598 for portable usage given the sound leak from the very open design. IMO, cMoy is not a good solution unless its specifically for travel. $60 for cMoy vs. $100 for a Magni -- well, I think its an obvious choice. Not really a fair fight given one is a desktop solution, but I don't think they compare in terms of quality.