For those of you that are told that the X-Fi Xtreme Audio is not worth the mod; um no. The processor may not be the greatest, but it's all on the digital side, not the magically (and it truly seems that way) diverse analog section. If you are a purist, it really becomes a matter of nuthead-scratching to determine which is better, because all ADA (Analog-Digital-Analog) is really is about, is chopping up the sound in to itty bitty pieces, messing with 'em for a while, and then reassembling them (kinda' like when you broke your moms favorite vase and glued it back together, hoping she wouldn't notice the difference). Some DA (Digital to Analog) chips are better at reassembling the pieces, but a purist will glare at you and send you to your room without dinner!
The most important part is the output OP (Operational Amplifier) amp, a good one is prohibitively expensive for competitive mass production. Some "nice" companies now put a $0.008 socket on their cards so you can use a different OP amp (sooo generous of them).
The stock OP amp is usually a 455x series OP amp. It was an amazing OP amp back in the late 70's, much better than the ancient 741! They are only made still because they are dirt cheap.
An inexpensive alternative is the TLE2072 (dual), it's much better than a TL072 (which is superior to the 4558) and it costs around $2.50. If you have a really good ear (I was a musician when I was a young man, so I do), an OPA228 (around $10) is very nice indeed!
Another good idea is the RF shield. Especially if the card is within 4"/10cm of another noisy card. It doesn't need to be fancy, just a well cut out piece of aluminum attached to the bottom of the card separated with aluminum spacers and mounted with screws. All the holes are grounded and feed-though so it is (almost) fool proof.
Capacitors: Well, a touchy subject. Yes they make a difference. In the case of this card though, make sure your computer has a high quality power supply (like an Antec: 'an dona' be tight with the coins). Try to route the wires away from any other devices and you should be fine. If you want to replace capacitors, all you can do is replace power filtering capacitors (like I said, a good PC power supply will take care of most woes), I suggest "Elna Silmic II" series capacitors, they are reasonably priced, reliable, and have good sound characteristics.
Filtering capacitors are not a big deal. Series capacitors are! the DC blocking capacitors (on all SB models of cards) are surface mount devices, and they are tiny little fuc... er frogs, they have a case size of 805 to 603 usually. Unless you are a master at soldering, forget about trying, and finding good replacements is a bitch. If you have the skill, "Wima" makes some very decent SMD capacitors!
I am a new member, so I assume that's why I can't post pictures of my wonderful mods?