Update: I replaced the power supply filter cap with the blackgate (man that thing is big); Here are my findings:
Actually, I'll keep it short. Not much. There might be certain situations where this cap will provide more of a reserve or possibly its emitting less EMF (who knows). This mod is not going to be one of those that you go "wow" from doing. I don't suggest it for the do-it-yourselfers. It's just not worth the result. The DC coupling mod IS worth it. I am having a very hard time detecting any difference with the new cap in, although I haven't done a lot of listening. These are my first impressions.
It WILL take an extra slot. The capacitor is nearly an inch long.
On another note, I added some EMF paper on the backside of the card. It slightly reduced some faint fan noise I was getting from the PC. I think this is a worthwhile mod on any card. It has a no risk factor and it's relatively cheap. It's never a bad thing to put this on the card.
If I had to guess as to a minor difference these mods made sonically. I would say that there is a touch more smoothness to the sound. Less grain and a touch less siblants. The detail is still there. Keep in mind, I cannot say this for sure. The degree change (if any) would be very small. I could easily detect changes from just about everything else I did to this card.
Overall.. it didn't hurt the sound..just didnt help much.