Even with the purchase of these control panels, you'll probably still need to pay someone with experience with the software to install and configure it so it works for
your site and doesn't look out of place.
I find that alot of template-sites (which are unfortunately usually linked to hosting companies), have the basic striaght-forward billing software template, which often looks really awful and has no link with the actual templte site whatsoever. It sometime leads people to think that the site they are 'paying' or 'checking their account on' is not linke to your site, causing them to bugger off and go elsewhere, which is obviously what you DONT want.
For that reason, I would reccommend that you purchase a decent billing software package and then let someone with experience manage the installation and configuration.
I can reccommend that you ask on these Forums for that, or make a post on a new forum that Open-Source developers in South Africa will soon be using which is :
www.LinuxOnline.za.net (go to Forums).
Regards,
~Equinox