A lot of discount paint places use single stage paint... it has the base, pigment, and a hardening agent all in one (eg, does not need to be clearcoated) ...I wouldn't do it.
I have a diamantschwarz car also, and the paint definitely needs to be in good shape with new clearcoat to look good.
(you alpine white II owners... damn you!!!)
Although it doesn't have anything to do with how my car runs, paint is one of the biggest things that effects how I feel about the car.
I didn't have the very best respray in the world, but I think if you can put away a little money each month, take the time to find somebody (eg, a body person with a home setup who can do it on the side), and schedule the time to fully prep the car yourself, you can get good results and give yourself a great platform.
for body work, a big portion of the cost is OPPORTUNITY cost, eg, if they take on your budget, pay cash job, they can't take on a high dollar, paid-for-by-insurance job. But, if you're patient and can find out when they are really slow (winter, etc.) you can get a good deal.
The qty of PPG diamantschwarz metallic is going to run you around $600 btw.
$400 of non-factory matched single stage would, in my opinion, drive you NUTS afterwards. Don't do it.