I need advice for power cords

In my experience the power amp has been #1, however that is not an option for you. I would go, preamp, phono stage or DAC and sub last. You should be able to get good cords for all used, in your price range.

Skip the sub amp. It will make a difference however slight compared to everything else. When you have a budget you make budgetary decisions and this is the first one- skip the sub.

Next after the sub amp, I don't know where people get this idea they need a power cord for this and a power cord for that. If the power cord is good it will improve everything, even the sub amp just not as noticeable. But listen, its not that it doesn't make just as much difference on the sub amp. Sorry, know that sounds confusing but bear with me. It makes little difference on the sub amp because the sub amp operates in only one very small part of the audio spectrum, and a part we are not good at discerning fine detail at that. 

Everything else though works all across the whole spectrum, including midrange and treble where our ability to hear and discern fine detail is exceptional. So do yourself a favor. Forget everything about a power cord for this, power cord for that. Focus on finding the best two power cords you can for your phono stage and pre amp. Skip the sub. I would also skip the DAC because there is sadly no way of making digital sound good so why bother? But that's a judgment call, not everyone has figured this out yet, its your money, your system, and so if you want to divide your $1k into 3 then go for it.

Anyway, that's the deal. Forget about components, concentrate on the best 2 or 3 power cords for the money. If you go with 3 then it becomes super easy, just search around and buy 3 used Synergistic Master Couplers. That will be right about $1k, if that. If along the way you find a $500 SR Blue or something like that, go for it. Put it on the pre or phono. Whatever. Just do yourself a favor and focus on Synergistic.