Definitely ifi zen dac in my opinion if you want warmer… also has the bass button. zen CAN the later upgrade can be bought later and stacked with the zen dac(which actually completes this stack combo as the zen can is the stronger amp and zen dac is rather good as the dac of the combo). The drop version of the zen can had a 6xx button even… they are quite good for those neutral headphones you want a bit more warmth for. as mentioned above me from sun_dyes the k5 pro is another option.
Be sure to keep an eye on used markets for your audio equipment, I say this alot but it can save you a lot in the long run… you can find absolute mint or even sometimes brand new equipment for much less than full price. Zen dac is usually $120 brand new and k5 pro is $150. The zen dac and can also have a balanced port… so you can grab some balanced cables on the 58x jubilee and run it balanced if you want… gives it a bit of a better sound of the zen’s nothing major but definitely more power