Well I ended up putting the original filter back on my 6.6gal so I had an extra filter and an extra heater. I figured that since I already had those things, and plenty of extra decor, if I ever wanted to get another betta all I would need is the fish and the tank itself...
So I went to Petco today on my way home, to see if they had any nice bettas. This really cute little marble guy caught my eye, and he seemed healthy so I took him home! :) I'm hoping that I will have better luck with him than the last betta I got there, who died in QT. Ammo is also from the same store though and he's doing great so I'm not really sure what to expect... I hope he does ok! I also bought a critter keeper and set up his own tank so hopefully that will help prevent anything from happening to him.
The water I put in the tank is a little too warm so I haven't been able to put him in yet, but I'm excited! He's so cute and I hope he likes his new home. I put the moss ball and banana lily from Ammo's tank in there so he even has a couple of plants too. I hope to eventually get him an anubias or something as well.

New guy and his future home!

Cutie! Need to think of a name!