nay, today gpu's like one's from amd have better audio than most of cards on market. (except sound blaster's for $100+) and mobo audio is not that bad anymore either... - if you have good mobo.
A 25 quid card probably won't make a significant improvement. Internal cards are said to suffer from all sorts of internal electromagnetic interference, being so close to other electrical components and as some of the Tek videos pointed out, none of the sound cards on the market have adequate technical documentation with stuff like Output Impedance.
If I were to give you some advice on reducing hissing/static - don't set your hardware output to 100%. A lot of the shoddier internal sound cards seemed to give away a lot of static at 100%, but performed fairly well at 50-80%. In my experience.
Also, don't use the front panel sound output. It appears that by the time the analogue sound gets from the card to the front panel, it looses a lot.
amd's 290x TrueAudio delivers quite good audio; (My comparison is between All-In-Wonder HD 3650, Sound Blaster card from 2008-09 and 290x -> 290x takes the win spot.)
nah its separate chip on gpu; its simply a sound processor unit. Before only on sound cards. Obviously its not going to have features of proper sound card to amp out output and other features - other so aggressively pointed out. Worth noting person who actually posted this was wondering if sound card is needed - he didn't provide that he has Surround Speaker system that requires a lot of power... with due respect most of user-base use their gpu's as sound cards or their mobos.
Only few people have speakers, and needs for proper sound cards.