your setup is fine, you wont benefit from a better setup
the razer actually has quite some dpi, ofc you can go for more but the difference aint that noticeable anymore
step from 400 to 1600 is huge, but from 1600 to 3200 or more there isnt a huge change anymore, just a small one
so if you want to save money, stay with your setup and buy an usb switch so you can use your mouse on the pc and the xbox without unplugging it