new juwel tanks should now come with t5 as standard - make sure and check you aren't getting old stock.
as for squeezing some extra lights into them, it's easier than you would think - I have 147w in my Trigon 190, and with a further mod could add 48w more easily.
however, if you don't need the tank to have a hood then it would probably be better to use a pendant with mh and actinics.
Juwel have been talking about doing marine 'plug and play' for yearsnew juwel tanks should now come with t5 as standard