OMG, please tell me you have something between your two boys or I may really just jump off a tall building in utter & total dispare...
Yeah $75 is pretty normal for a tank up here in the north - all the fish stuff around here is darn expensive - sorry to burst the bubble on that one
. I would suggest you look for an eclipse system, they are really good filtration & relatively low maintance. I actually opted to go for the slightly cheaper waterhome system which was a BIG mistake... I killed the filter in no time & the tank has a bad bacteria infectoin I can't get ride of ... and... and....
Eclipse system is probably the best deal if you want a starter-tank
Also there are those 3 gallon tanks that come with a betta-divider & are florescent colours... if you have no idea what I'm talking about (I can NEVER remember the name...) that's cool - but they are a pretty good deal too.
As for heat, make sure you buy yourself a good thermometer before running out & finding a heater. Sometimes you don't need to do anything but move a hot-lamp over the tank.
I would not suggest putting another fish in there - even with a filter because the tank will quickly become overstocked.
Temperature should perk him up alot - but he may be ill, so keep a watch on him for the next few weeks.
Good luck,
Nes.