Mine is going satin black. Had words with our paint suppier at work and he has sourced me some light commercial paint. It's durable, thick, a direct product so no need to prime. And to make a satin or matt finish you add a matting agent, so if you need to do a blow in for accident damage you need to get the mix spot on or it won't match, this paint I'l be using comes in gloss levels off the shelf.
Gloss black would be a nightmare and needs massive amounts of prep work as it shows every ripple and imperfection. You'd be looking at least £300 per panel for the prep alone for a proper job (not half the stuff you see at shows thats shiney but goes up and down like a ploughed field)