For most people, the speakers (or headphones) will always be the weakest link. I find it funny how many people discuss these things on youtube, claiming that a $50 basic Sound Blaster card is night and day compared to their integrated one, and the speakers they use are cheap Logitech or Creative multimedia speakers. Also, I'd argue that for testing the quality of sound cards, using headphones is a bad idea. Generally I find that good quality hifi speakers provide a much better listening experience than headphones. The positioning of the different sounds stand out much more clearly in the sound image when using a good quality amplifier and speakers. It's all a matter of preference of course.
And if you EVER find you want to use the bass/treble controls (or much worse... Loudness *shrug*) then forget about the quality of your sound device anyway, cause you're not after natural "clean" sound in the first place.
That, I think, is probably the essence of sound in general. People like different things. Some people want super heavy bass that makes their floor shake, others want clear midrange and open highs that provide a detailed and "airy" sound image with clear holography... Neither is "right" or "wrong". Only different.
WinXP : PIII 1.4GHz, 512MB RAM, 73GB SCSI HDD, Matrox Parhelia, SB Audigy 2.
Win98se : K6-3+ 500MHz, 256MB RAM, 80GB HDD, Matrox Millennium G400 MAX, Voodoo 2, SW1000XG.
DOS6.22 : Intel DX4, 64MB RAM, 1.6GB HDD, Diamond Stealth64 DRAM, GUS 1MB, SB16.