When I sit and idle allowing my RX-8 to warm up, when I get into the cab it smells like fuel. What could be the reason? anything serious? I've seen in some forums people saying this happens due to a clogged cat, Can this be the case? If so what are the downsides of it other than the smell? Any other side effects?

 

Did you notice any CELs?

First be sure you have no actual fuel leaks, pull up your driver side rear cushion to check your fuel pump ring isn't leaking.
There is a recall on them.

A clogged or broken cat is possible.
Raw fuel smell means you may be having misfires, if that's the case you need to inspect your cat ASAP.

Misfires kill cats, bad cats kill engines.