Unless you have a setting, driver, or software issue there is no reason your onboard shouldn't be able to run the GSP 302's at volume. As far as DAC/AMP's that depends on your primary uses.
GSX 1000 $180ish
+Headphone and Mic Input with sidetone and mixer settings
+Hella nice touch controls
+5.1 and 7.1 virtual surround
-Lacks power, anything more than 60hz and you find yourself using close to 80% if not more.
-Software is unstable on some systems 😕 but has plenty of options and control provided it doesn't crash constantly.
Soundblaster G6 $130ish
+Headphone and Mic Input with sidetone and mixer settings
+Can run any headphone or IEM " Low gain and High gain amp output"
+ 5.1 and 7.1 virtual surround
+Scout mode is awesome in FPS games
+Software is stable with tons of options and control
+ Music under direct mode sounds a bit better over the GSX line
-Sidetone and mixer settings that are not as easy to use as the GSX1000
-Toggling 5.1 and 7.1 isn't as easy to do as it is on the GSX 1000
-Surround Sound is okay but not fantastic
Fulla 3 $99
+Neutral sound that is better than the above units
+Headphone and Mic Input
+Can run most headphones
-Lacks any software
-Lacks any perks for gaming " Software bundle, Scout mode, Surround sound"
FIIO e10k $75ish
+ Clearly a winner for music over the G6 and GSX
- Lacks any perks for gaming " Software bundle, Scout mode, Surround sound"
-Lacks a Mic input
Clearly different products for different uses.