First of all how would the coilovers work with 16" rims as opposed to 17 or 18s? And, where can I buy the rims from especially a custom painted version? (webste wth prices preferred)

 

all of them will fit the same the only thing you need to worry about is the width
If your's is a daily driver I think you will like the 16" better
The 16s weigh less so you don't over work the struts
b/c they are lighter they have less rotaional mass so you can accelerate better.
16" tires and wheels are cheaper for almost Identical performance in sidewall flex
the ride is better with 16" due to the slightly taller sidewall
the sidewall flex is the only drawback as opposed to the 17". but the loss is so minimal on most cars you won't notice.

I don't know about custom paint. you could buy them and have them painted

http://www.wholesalehyperformance.com/wheels-new.html
then scrol down in the left frame to VolkRacing. It's like 3rd or 4th from the bottom

 

Thanks, what width would you reccomend?