Decisions, decisions, thanks for the info guys, plenty of options.
TBH I don't really want to fit an amp and subs, I have a load liner in place anyway, but I'm not ruling it out completely!
I will do the measuring when I get back home.
IIRC the Sony head unit is 4 x 50 anyway, it's the Explode model with MD slot.
I would deffo need new tailgate struts (beefed up) if I was going for the big install

Cheers
Jon