I assume this is the kit? http://thegardenpet.com/index.php?ma...roducts_id=341
It looks pretty nice to me, I would probably get it if I had the room, $15 cheaper for a tank twice the size? yes plz
The heater is great, if it really is 100W, I believe 100W heats up to about 40Gal (where I live anyway) so if you ever need to upgrade to a 40 Gal, you don't have to buy another heater. It also doesn't appear to be overpowered, somebody please correct me if I'm wrong!
Not too sure about the filter, Betta's like water with low flow (some people's love to play in the current though!), so if you think the filter is a little too strong, or your betta is having a tough time swimming past it, there is a guide on the forum to teach you how to correct it: "DIY Filter Baffle": http://www.bettafish.com/showthread.php?t=30139