Looking to upgrade my audio game, but which headphones do I pick?

I currently have Razer kraken pros and the mic died. I went with a zalman clip on mic as a temporary solution. I plan on getting a new set of headphones, but I can't decide between the sennheiser 558s or the hyperx clouds. And if I did get the clouds would the mic be better than the zalman?

558s will sound better than the clouds. I have the clouds and expect their mic would sound on-par with the zalman clip mic.

the real question you have to ask yourself between those two specifically is open vs closed back and if you're willing to sacrifice sound quality for the convenience of having everything rolled up in one (hyper clouds). The 558s sound nice but are open, so if you game in an environment with lots of noise, will probably not be favourable. they also have a (large?) soundstage which is good for competitive games like cs:go. a combination of the 558s and a modmic will likely be infinitely better than the clouds, but without knowing what games you play, music you listen to, etc. it is difficult to judge whether there may be something better for you specifically out there.

I think I'll wait for a sale in the 558s and upgrade to a modmic after a while. Also, would my motherboard be able to drive these things or will I need to invest in an amp?

It's only 50 ohms to drive so you should be fine without an amp.

I have tried both, the 558 will sound a lot better than the Hyper X cloud in games as it's open, the positional benefits will be profound. The 558 also uses the same driver as the 518 and sounds virtually the same.

Grab the HD518 and a ModMic is my suggestion, or just keep using your Zalman if you are happy with the quality.

The mic quality on the HyperX isn't terrible but it's not great either, have a search on youtube for some mic tests of it if that may help make a decision.

Onboard audio will drive HD5xx headphones just fine if you have a reasonably recent one with something like Realtek ALC 892 or 1150 on it.

Have you considered checking out the AKG k553 pro studio headphones Albert did a video on? They're currently $120 on massdrop and at that price they're a steal. I bought a pair myself.