I'm not saying that standalone DACs are superior to analog by itself, I'm saying that they are superior to internal soundcards aslmost universally. Also the bifrost does bitperfect conversion, meaning no upscaling.
actually this isn't necessarily true. the issue, as i alluded to before is noise. _in general_ there are more sources of noise inside the case than out.
generally speaking, there are two sources of noise when you colocate your D/A stage with your computer. 1) EMI 2) switching noise from the PC's power supply
the reason people generally try to do D/A conversion out of the case is that moving out of the case is the most reasonable way to avoid both sources of noise. EMI is generally blocked by a sufficiently thick case, and the PC's power supply can't inject noise on your D/A's power rail if it's not powered by it.
that said, nothing's stopping you from doing both within the case, and if you look at pro audio cards such as the m-audio line, they deal with EMI by shielding their cards, and regulate the crap out of power from the power supply to stomp out noise on the power rail. in exchange, they get massive bandwidth from being on PCIe.
it's also worth noting that you can fail at both these things on an outboard device too. this is why, eg, usb devices don't always sound that great. not only do they have to deal with bus noise, traffic, and corruption, but it's not like the only source of EMI is your computer... further, usually _if_ they have outboard power supplies, they're switchers that are just as noisy as your ATX job, and lower voltage to boot. spdif doesn't completely fix this, but at least gets rid of the bus aspect. still, you have to keep resampling, jitter, etc. in mind if you go this route.
anyway, my point was that nothing's perfect, and you shouldn't feel like you need to rejigger everything and buy all kinds of audiophile gear because someone on the internet tells you that your sound card is junk.
my "perfect" setup (ie, the one i can't find enough flaws in to give a piss) is a pair of infinity ref1's (ca. 1989) i got free and refoamed, a lepai ta2020-based amp that i hacked the input section off of (the volume pot died, oops), and an amb gamma1 kit that i leave usb powered. the headphone end of it is a meta42 kit and a pair of senn hd600s (pushing 11 years old this year!).
at near field, this is about as good as it gets, and the largest investment was in tools and time to build and learn.