I have the ALC 1220 on my motherboard. I own a SoundBlasterZ and I also own a Asus Strix Soar. I am VERY picky about sound quality.
Honestly you might think your sound is good with on-board audio - but the SoundBlasterZ or Asus Strix Soar absolutely DESTROY onboard audio (unless its the creative) PERIOD. In my use the SoundBlasterZ was best if your gaming a LOT, it's really strong with gaming and giving a great punchy bass to explosions and the headphones are amped up pretty high. The Asus Strix Soar didnt have quite the bass punch in games, preferring a smoother rounded bass. The Soar was best for movies and music, it gave a better overall impression and staging to sound without being too aggressive. The soar is what I am currently using - I think it's an ugly sound card but it has a Texas Instruments DAC and one of the beefyest AMP's on a sound card I've seen. I only stopped using the SoundBlasterZ because of driver conflicts with my motherboard but it was an EXCELLENT card.
All these options beat the pants off on-board sound. You can look at your motherboards sound output chips (usually on the lower left region of a mobo) and just look at the capacitors. Their usually garbage and too small to create any reasonable bass. If you like big bass you want big caps - thats when most of the current draw happens.
With your onboard sound card get a few different headphones plug them in and just listen to the silence. Then start a program that puts a load on your CPU and GPU without any sound. Do you hear any buzzing, beeping in the faint background. Some headphones wont expose this. I have a pair of BOSE that will. Its electrical interference over your motherboard and its very difficult for sound chips to isolate. Creative labs has done an awesome job preventing this though.
EDIT: UPDATE
Im going to have to redact some of what I said about onboard sound. I put the ALC 1220 through the paces and ... wow. It was WAAY better than I expected. Strange it has an AMP gain function for headphones that Ive only seen on the Asus. So what the hell lets play some BF1 with the on board sound (Gigabyte x399 Gaming 7 blah blah)... It sounded flipping wonderful. The Asus will get WAY louder and drive much more aggressive BASS but the ALC 1220 isint too far behind at all! And the best part is there is zero buzz. The Asus did have a tiny amount.