Upgrade for KZ Kastor

I am currently using KZ Castor (bass boosted version). The KZ are my first ever IEMs and I am ready to a plung and go for something more espensive. Seeing there is a nice sale also going on. Now i need some advice on what could be best upgrade. My budget is around 7-8k INR but i can stretch it to 9 maybe 10 but I'd prefer to stay in the 7-8k range.

I like to listen to alot of synthwave. So i need something with nice bass. So please help a homie out here.