I've been researching information on PC audio hardware, and it seems that there is an agreement that some PCI sound cards complete with AD/DA converters are available for obtaining hi-fi quality audio from either PCs or Macs. I am an ex-Mac person and have switched to PCs in the last few years. I have no intentions of going back to Macs either as I believe PCs are a better platform for music, and for developing a high quality, quiet PC system as a music server.
These PCI-bus cards are available for Mac and PC use:
Lynx Studio Technology 22
Lynx Studio Technology 2 (Versions A, B or C)
Digital Audio Labs Card Deluxe (Stereophile Magazine recommended)
All of these cards have received excellent reviews with the Lynx cards at the top of the range in terms of cost and performance. The Echo Mia is about as low (approx. $200 street) as you will want to go and still get very satisfying sound. I'm sure there are those who really like Terratec cards, but I don't know too much about them. They are all capable of providing 24-bit/96 kHz digital audio for quality, uncompressed stereophonic reproduction (16-bit/44.1 kHz for CDs). The Lynx 2 has an internal clock that definitely reduces jitter and improves imaging. It not only offers balanced analog input/output, but also digital S/PDIF input/output. The Lynx 2 was really developed for quality audio mastering purposes, which make it suitable as a PC audio playback device.
You'll have an easier time getting driver updates for Windows PCs than for Mac OS X machines. There are more PC users, so hardware manufacturers will often place more resources in developing Windows driver updates first.
Chassis and Hardware:
This is what really makes PCs a better platform for PC audio. You can purchase a high quality, aesthetically appealing and thermally conductive Aluminum case that will fit in with the rest of your hi-fi gear. Some even have heat sinks and no fans for ultra-quiet operation (like Hush Technologies ATX case). If you search Google under "htpc case," you will find some wonderfully designed and well-constructed full-sized ATX motherboard compatible chassis. With PCs, you have the option of specifying your motherboard (Intel chip set motherboards are highly recommended for stability), processors (single or dual), media drives (CD, CD-R/RW, DVD, DVD+/-RW), quiet PC power supplies and cooling devices (fans, heat sinks, heat pipes), quiet and fast hard drives (SCSI in any flavor if you want freedom from possible hardware conflicts), sound absorption materials, quality connection cables to improve internal air flow and signal quality, and an infrared remote for the bon vivant. The combinations and possibilities are endless to come up with a hi-fi PC system that not only sounds good, but looks good as well.
At one time, the Mac was the only platform for iTunes. Apple got smart and developed iTunes for Windows. MP3 audio stinks, but if you want it, you can get the best of it from Apple for both the Mac and PC now. Windows Media Player is also available for both platforms, but I suspect Microsoft will always take better care of Windows users (remember Internet Explorer for the Mac?). The PC platform also has Musicmatch Jukebox, which is a great media jukebox for organizing and playing PC music files.
The PC has more software titles for uncompressed, high resolution audio file editing (reducing noise from analog transfers, digital amplification/normalization, signal compression/expansion). Three excellent editors are Sony's Sound Forge, Adobe's Audition and Cubase's Wave Lab. Audition is a bit more complete with noise reduction and Red Book CD burning, but Sony does offer additional professional-grade software for noise reduction and Red Book CD burning applications that can be used in conjunction with Sound Forge. Even the freebie open source application, Audacity, is capable of basic audio editing and it accomodates freebie VST add-on applets for sound editing. The Mac has incredible applications like Peak Bias and Logic Audio, but they are more expensive than their PC counterparts. Add-in options are very limited as well.
Basically, Windows-powered PCs offer more options to get you to hi-fi PC audio nirvana. As with anything, you get what you pay for. A high quality PC audio system with an audiophile enclosure with quiet components will run over $2,000 (a lot more if you go with dual Intel Xeon processors, two SCSI drives--one for Windows and applications, the other for strictly holding your valuable music collection, and a quality sound card like the Lynx 2), but you'll have a system that will not be obsolete, but upgradable.
One thing to keep in mind is that there might not be hardware and software available with Windows or Mac OS X for processing SA-CD data at this time. If you have a large collection of SA-CDs, you may want to keep your SA-CD unit around for playback purposes.