I need to get an antenna combiner for mine still..
I fitted a fan to mine, but think I'll probably look at fitting a bigger heatsink aswell when I get around to it. It isn't as glitchy at the moment, but it's still not as stable as my old one. I still think it's mainly down to the USB bus, and power on the USB system, as it seems to mostly have issues when I have the 3G modem plugged in, and more so again when the 3G signal drops.
I swapped my passive crossover system to one of my DSP amp conversion boards, so have P38 amps in the loadspace, and I went with the resistors for attenuators off the amplified feed from the head unit. The sound quality is so much better now - I don't get any buzzing or noise in the speakers either.
The only thing I do get, which I want to try and find a solution for, is what seems to be digital noise from the head unit into the subwoofer. but balancing transformers might help..