Well done Zunglam

you are much braver then me

I had the help of a friend who knows how to work with wood and Moonfly who has been such good help using Winisd without both I think I would have bottled it SO HATS OFF TO YOU SIR
£202.00 for the inuke3000 :-0 I paid £227 so a good deal for you there.
As for ported or sealed, Sealed will be easier to build and model but there are some very cleaver guys on here that will guide you regarding port size and air speed velocity :~0 what ever all that is

Vinny gave you some good advice on that one regarding QTC values..
I know Moonfly was saying around 60 Litres for a single 15" sub but I don't know anything about the SSD drivers so Am at Bladeice will help you there, I still say buy two 15"s and build two cabinets one for each corner at front of room and you will not look back.
Also it may be worth while asking if you can get all the MDF cut to the desired size then you can glue and screw it together ? Wood working shops can get a cut list together i.e main box, brace, baffle including cutout for the drivers, "though it will be better to have the driver at hand to work out size from.
Good luck and if I or Tim who built mine can help we will :-)