Well, happy birthday!
As far as communities in 10 gallons, it's rather a struggle. You can't really fit a happy shoal of fish in there with your Betta, eventually they will get nippy and unhappy because of space restrictions and then will turn on your Betta which is no good! The only thing you could really do is have 3-4 julii cory's or some other smaller corydoras with him but I'd personally just split it!
I love my split 10, in fact it's split 3 ways still giving each fish 3.3 gallons! But split in half was wonderful as well.
I caution against buying kits, it's probably going to cost you more money in the end if you do because then you'll just buy replacements of everything that it came with. Well at least that's what I did. I hated the whisper 10i so I got an Aqua-Tech 5-15 from wal-mart, baffled it and it works great! The bigger filter really won't hurt him if you baffle it well
Here's a water bottle baffle that I use: http://www.bettafish.com/showthread.php?t=30139
and here's what mine looks like on my 5-15: http://s1292.photobucket.com/user/li...ilter%20Baffle
This allows the water to go out the sides and therefore circulating the water through the tank better and easier. Also you can do this sponge filter, not a step-by-step but if you read the comments you get what it's telling you http://www.bettafish.com/showthread.php?t=56100
I even changed out the hood too to an LED light strip which I don't like because it doesn't grow plants well so if you get a regular hood you can replace the bulb with a small CFL to grow plants well
But these are all my experiences, I also suggest you get an adjustable heater too for those just-in-case moments of disease or something. You can find them online for cheap, I suggest this 50W heater: http://www.drsfostersmith.com/produc...8&pcatid=11368
So yeah, I think you should just get the 15 dollar regular tank with nothing in it, get a hood and get your own filter/heater so that you don't have to buy everything twice