First off, I wouldn't say that you're an "audiophile" so much... but you look like you're interested in becoming one. The term is more for those who are picky about their sound, and that will kind of develop over time; it isn't necessarily a term for someone who wants things to sound vintage, or "cleaner." More or less, it's trying to recreate the original sound intended for the listener, which is usually a foregone thing by the average consumer. With that said, welcome to the community. Learn to get picky with what you hear, and be ready to throw some big bucks at this hobby.
If you don't have a lot of money to spend, and you're looking for a nice sound card to give you balanced outputs, get something that is designed for studio use. The
Focusrite Scarlett 2i2 will give you a quality USB card without sacrificing output quality, or too much money ($150). Run this with an ASIO driver, and you can use the proprietary software to check that your output isn't clipping when listening. Just make sure you don't use the software discs included in with the sound card, and download them from the website; that will save you a lot of time from having to install all the updates/patches/etc..
When it comes to what cables to run from the sound card to your amplifier, use TRS connections at a minimum; they are shielded, and will help prevent your speakers from picking up electrical noise through the cable. If your amplifier doesn't support TRS connections, then it won't matter if you use TRS cables or not; however, it is better to have some on hand, in case you upgrade to one that does support it. TRS is basically the more cost efficient, 1/4" alternative, to the XLR connection (XLR, itself, is overkill for home audio purposes). The wiring from your amplifier to the speakers will usually not be shielded (typically bare wire connections with older speakers), so keep the wire length to a minimum; 10 foot runs are about the most you should go before you start risking some noticeable noise. RCA is also acceptable for delivering sound to your speakers, although it will still give you an unbalanced cable, so don't run them for long of distances (same length as typical speaker wire, though you can occasionally get away with 15' runs, depending on if there are power cables nearby/etc.).
If you want flat sound to come out of your speakers, without noise colouring, consider investing in some studio monitors. Most monitors do have colouring, but they are much more minimal when compared to your typical consumer speakers. Monitors will give you a much clearer sound that is closer to the original sound intended to be heard by the producer. With vintage speakers, you will get a warmer sound, as they are heavily coloured; however, the sound is typically much more pleasant than modern consumer speakers. Find what sound you like, and stick with it. Personally, I enjoy vintage speakers for casual listening; however, with everything else I do, I have to have studio monitors. Cabinets that are for outdoor use are not ideal for indoor use; keep that in mind.
Modern consumer speakers will never deliver the same audio quality that vintage, studio, and audiophile equipment will give you. Modern consumer speakers will typically use the cheapest drivers available, while meeting a particular minimum requirement, and usually have very low quality wiring for connections. Sound bars, and all the other "high quality" marketed items you'll run into (like Bose, Beats, and so on) will typically be overpriced and leave you wishing you didn't waste your money. The best quality does not come in consumer form; it just can't, for many reasons. When it comes to tube amplifiers, these do cause sound colouring and distortion; if you want sound quality, avoid tubes. If you want the original tube sound, there are options... but they're either synthetic (digital), or relatively expensive.
When you buy/download music, be sure to get lossless file formats only. While many people do not hear the difference between 320k MP3s and lossless formats, that is typically due to one or more of the following reasons: speaker/headphone choice, impedance of the speakers, gain/volume, style of music, hearing loss problems, and if they actually have heard the music before on other equipment. There is a difference between lossy and lossless formats, but some people just can't hear the difference. What's most common in "comparison tests" is to use a track that is never heard before by the listener. The problem with this is the listeners have no idea what to listen for. While this sounds like a facile argument, it really isn't. Lossy formats actually dampen certain frequencies when trimming the "unused" portions from the file (in essence, that's how the compression works). If you listen to a familiar track in mp3 form, and then switch to FLAC, with quality speakers, you will notice some very interesting differences. One great example I've used for explanations is the track Aenima, by Tool. Depending on the listening circumstances, you will hear some very unique differences between the two tracks. With music like Tool's, you can pick out certain instances where background instruments are more pronounced in a lossless format, and are cut out/muffled in the lossy formats. It all depends on how much of a stickler you want to be. For me, I usually notice the difference when the volume is turned up. At a certain volume level, the subtleties start to stick out like sore thumbs.
One reason some people won't hear these differences is because of hearing loss. There are many who suffer hearing loss in certain frequencies for various reasons, and plenty of people do not know if they suffer significant hearing loss until they get tested in an isolation booth. People will lose hearing in the higher frequencies as they get older, and this causes clarity problems; hence the famous "What?" you occasionally get from the elderly. People who frequent loud environments have the same problem. Those, like myself, who have suffered low frequency hearing loss will have a problem with hearing things in terms of volume/loudness (lucky me!). But I'm getting off track...
Start slow, and build your audio selection carefully. It's better to be selective with your hardware, and wait for the right price on what you want, than to have buyer's remorse. The serious audiophiles are stubborn for a reason; we want what we want. Hopefully this helps you a bit with getting started. Google will be your friend with this hobby; just be sure to look for reputable sources, and stick to the audiophile websites and forums. Pick an audiophile community that suits your style, and don't get too discouraged when you can't find what you want... it will eventually pop up; be it information or hardware.
Important notes to keep in mind:
Keep your audio power on a separate circuit (if possible), or at least on a different outlet.
Use a power conditioner to help keep clean, even power delivery.
Keep your audio cables separated from your power cables.
Invest in cable cuffs, or something similar; zip ties will be a huge hassle when you need to rewire something.
Cheap power strips with surge protectors are a big no-no. Look for a quality brand; you get what you pay for. No sense in frying your components because you bought a cheap power strip.