The Cayin C5 is actually known as a good amp that can power both the SZ 1K's and 2K's. so if you already got that amp, no need to buy another one, cause you should have enough power there. In regards to software EQ, it really depends on what device your on. Computer? I highly recommend Equalizer APO if your using Windows. Its a system wide app, and it works amazingly, just remember when you juice up them frequencies, you gotta bring the gain down, or distortion and crackle lackle, will become your #1 enemy. If your going portable on your phone, I have had great luck with Neutron and Power Amp. Although I do believe that Neutron's EQ works a bit better, but out of the box you will only see 4 bands. I didn't realize until I went deep into the options that you can select a 10 band EQ, which is good, cause you get the real low 34 hertz slider all the way up to the impressive 16K slider.
Ultimately the best EQ is hardware based, as that way your not relying on your computer's or phones built in DAC, which in most cases is crap. I am using a vintage Realistic 12-band equalizer and this puppy can pump out the power, its got a mini transformer inside that would fool you by its size. But the fact that I have to put the output gain down to minus 16 tells you a lot lol. Its because if your already amping with your amp to the cans, you don't want to double amplify, otherwise here come crackle lackle. Yep, I agree, we are the saddest sons of b***** the worlds ever seen.
But we like our bass way down low low low low low low low <<<---that was echo for draumatic effect.