I don't understand what you mean. ATX is the standard motherboard size, therefore it is by definition "full size".
There are boards that are larger than ATX, but these are usually top-end boards where more features are being crammed in (or in the case of dual socket boards a lot of extra kit).
Do you mean M-ATX boards over ATX ?
I would certainly suggest going for a bigger case.
If you like the look of the P180, the P183 looks very similar and supports ful ATX boards.
I went from a p180 to a p193 which I'm very happy with.