Sound wise you must remember sound blaster comes whith its own software to customise the sound.I dont think it can run passive speakers like th smsl and the smsl has more power and features for the money.
I own the X7 and SMSL Q5 Pro. The X7 produces noticeably better sound with above-average passive speakers. In addition, the X7 has an excellent headphone-out and a software interface (via Bluetooth connection to a phone, tablet, or PC) that provides sound customization, including EQ, subwoofer crossover frequency, and volume level. The SMSL AD18 does not have a SUB-out... but can be used without a separate control device - unlike the X7, which requires a phone, tablet, or computer with software installed.