Okay, tanks in all.....
ONE divided ten gallon (the other for my nephew),
Two males seems like the best solution. I like the symmetry of two long-finned beauties on each side of a divider.
TWO 20 gallon regular,
One I would turn into your sorority tank and add a couple more girls and a bunch of cories for a lightly stocked, low maintenance tank that still has plenty of activity and life.
The other I would use to house one of the aggressive girls or one of the males and do a community tank with some pretty tetras or livebearers and some more bottom dwellers.
ONE 20 gallon long,
I would divide this into 5 and use it to accomodate the remaining 5 males OR 3 of the males and the two aggressive girls, if they aren't suited for community life.
ONE 40 gallon,
I would put the remaining betta in here, unless it is a betta that freaks out in large spaces, in which case the 1.7 gallon would be better. If no betta, I would do a dwarf gourami or maybe even a lace gourami as a centrepiece, with rummynose tetras or cherry barbs and a clown pleco. Yes, it's expensive, but they so purdy.
Another option that could look really nice if you like species tanks would be one massive school of tiger barbs.
ONE 66 gallon,
Something a bit different. A Jack Dempsey, Angelfish or some Discus would be amazing, or maybe a convict breeding tank. African cichlids could also be really cool. There's something really pretty about some stark white Texas Holey Rock against green java moss and crypts, then an explosion of colourful blue and yellow cichlids. Or a low-light tank with glass catfish. Congo tetras are another stunning option, or Bosemani Rainbows.
FOUR1 gallon bowl/tank thingers,
Hospital/quarantine tanks. Or you never know when you'll just *have* to buy that betta...
ONE 1.7 gallon marineland bow front...
I'd use it if any of your bettas aren't comfortable in larger spaces, or if you need to buy a new betta.
BETTAS:
7 males, 4 sorority females, and two aggressive female bettas not meant for sorority life :/
So.... how do you think I should go about sticking who in what and what in where? :lol:
Why so many tanks? 'cause I'm cool like that

Actually it's because I found some wicked deals, such as a free 20 long, a 10.00 66 gallon and a 50.00 40 =D Now I've got so many ways to put stuff... Any ideas? and even stocking ideas (must be betta fin friendly)??