One guy reported that he was banned due to a 12v fan mod, which may or may not be true. One thing is for sure, you don't need to worry about it. I'd wager half of the modded 360s on this site have the 12v fan mod, and there have been no other reports of bannings based on that mod. Some people speculate that M$ may be able to monitor the voltage that the stock fans are running at over Xbox Live, but if they can, they certainly haven't taken any action against modders based on this information. They definately can't tell if you have extra fans or leds. The only thing that you can definetely get banned for is a modded firmware, and even new stealth firmwares are good at avoiding that, but you don't need to worry about that. As for the cathodes or anything else using too much power, you have AT LEAST 30 watts to play around with. The 360s psu produces quite a lot more power than it actually needs. So you can run all of your extra fans and leds from power sources on the 360 mobo. In short, you don't need to use a seperate power supply or worry about getting banned for any of the mods that you're attempting.