You should just stick with an external solution since it's less prone to interference from the PC. If you think it sounds different for the better, though, then I don't see what the problem is. I wouldn't buy sound cards since most of the time, they just make your PC sound worse. They're only good for amping and when your onboard audio is pitiful, which is fairly situational. External equipment will pretty much always beat a sound card.
How many sound cards have you tried or is this just irrational "hate" towards gear that is marketed for gaming?
There is no reason external would sound any better, EMI shielding is cheap and it will eliminate all interference at least all audible interference as far as i know.
Actually the Creative Sound Blaster Z has very nice EMI shielding covering all of the circuit.
Also Price to Price comparison, most Internal cards wins in my opinion. Some internal sound cards are even recognized by audiophiles like the Asus Xonar Essence STX card.
I feel internal sound cards are often overlooked because they are geared towards gaming most of the time. But the only "gaming" part about them is the software giving you virtual surround and so on.
USB solutions usually cost more.
They often have exactly the same hardware as internal sound card but price can be as high as twice as much.
Only real difference is that USB does not need shielding like internal devices.
Edited by Notus - 4/20/14 at 4:13am