Bass sub ideas for high spl and deep bass

I am searching for subs to replace my punishers as i am unimpressed with their spl and how deep they go as while i mostly play hard electronic music i do like to play dub and reggae too. Id be open to 18 or 21 inch drivers and i wouldn’t want the driver to cost more than £500 really, i like the skram in terms of size, sound although the driver is expensive with the cheaper options still being over £500. Does anyone have any other cabinet ideas that will go low (30-35hz) and has a high spl while being no bigger than 1m length and depth? 

Thank you