I'm almost 100% positive you'll need another ballast to run higher wattage bulbs. Most ballasts are made for a certain max wattage and won't run more than that. If you had a ballast that would run 96 watts or 2 96w lights, then you wouldn't be able to use 55w or 65w bulbs in them because it would try to push 96 watts out of each (or something to that effect). The only exception is 55 and 65w bulbs. They are interchangeable and if you put a 55w bulb in a 65w fixture/ballast, then it will push out 65 watts...no problem.
Hard to explain and understand (for me atleast), but hopefully that helps some.
If you had the room over the tank, 2 96w fixtures would have been better. It would still be medium light and you'd still have some plant limitations, but its better than the 2 65w fixtures. Even better than that would have been T5 HO (high output) fixtures, which have better penetration in tall tanks.
I wouldn't suggest trying HC with 2x96w.....I just don't think it would do well at all. It tends to brown and die in under about 3wpg and without co2/ferts. It also grows best IMO in a nutrient rich substrate (not sure what yours is...).
Since you already have the 65w fixtures, you should just get plants that will grow well under them. You could try Java moss on rocks and line they up in part of the foreground to have a unified section, I guess, of Java moss. Wisteria is a stem plant that can be "trained" to grow horizontally. Play short pieces of it in the foreground and trim it when it gets too tall.....eventually it will get the picture. You should have enough light for that. You could try HM (Hemianthus micranthemoides), which is a bigger version of HC, but I'm not convinced it would do well, especially if the tank is tall. It would be worth trying though....just don't let it get shaded.