Okay, so you have 2 options.
1. Keep using the Sennheiser g4me zeroes and get the sound blaster x7 which will be powerful enough to drive them.
2. Since you said the mic is no big deal but you may need one in the future, get an easy to drive open/closed back headphone to use with the mixamp which is compatible with a vmoda boompro. This way you can use the normal headphone cable that it comes with plugged into the mixamp and when you need to talk in-game just switch the cable to the vmoda boompro and connect that to the mixamp. This means the headphone you get MUST have a detachable cable and it MUST be compatible with the vmoda boompro.
Open headphones, easy to drive, compatible with boompro:-
Philips SHP9500 - best bang for the buck headphones ever, easy as crap to drive, plug straight into mixamp and turn on VSS. When you need to talk swap the cable with the vmoda boompro and plug into mixamp.
Philips Fidelio X2 - absolutely awesome and super fun headphone, easy to drive, plug straight into mixamp and turn on VSS. When you need to talk swap the cable with the vmoda boompro and plug into mixamp.
Superlux HD668B - cheap as hell but don't let that fool you, these are absolutely amazing for the price and a steal. Stock pads are not comfy so you need to replace them with HM5 velour memory foam pads. Easy to drive so plug straight into mixamp and turn on VSS. If you want to use the vmoda boompro with these you will have to use a 3.5mm female to female adapter.
These 3 open back headphones already have incredible soundstage and imaging, when you plug them into the mixamp and turn the VSS on the soundstage will get even wider. Fidelio X2 is the best one here and also the most expensive.
Closed headphones, easy to drive, compatible with boompro:-
Audio-Technica ATH-MSR7 - surprisingly amazing soundstage and imaging for a closed back can. Easy to drive so plug right into mixamp and turn on VSS. Also compatible with boompro so just switch to that when you need to use it for chat.
Closed back headphones compatible with the vmoda boompro are very rare, ATH-MSR7 is the only one I'm going to recommend because it's the best for it's price.
This is really all I can think of and I don't really know what else to suggest, I'm out of ideas. These really are your best options. If you want open go with Fidelio X2, if closed then ATH-MSR7 then just get a vmoda boompro in the future when you need it. Open or closed, they will be absolutely amazing and you will get exactly what you want.