Different Styles For (Single.php)

I need to set a different style for single.php under a specific category, now Im aware that its easy enough setting a different style for Archive.php, though I need to go one level deeper. Is this possible? I have been doing allot of searching and have not found anything, I am ready to just launch a subdomain and a new install to achieve what I am looking to do, but the only problem with this, well problems is, I only need the additional single post template to ad one feature, a reviews plugin and I dont want to have visitors have to register with two accounts just to review products in a reviews section.

Or maybe there is a way to tell WP if in whatever category add plugin, if not dont, I dont know Im really lost on this one and would really appreciate the help.

Thanks in advance….