Here is a photo of my 6 gal betta tank at work.

http://www.nippyfish.net/6%20Gal.jpg

It's an Eclipse cycled with a power filter w/ biowheel, 25 watt heater
and air-stone. The air pump does give off a very faint sound but there
is a great benefit to cycling your tank even if it's "just for a
betta." If you end up opting for an uncycled tank you'll be spending
more time doing 100% water changes and testing for ammonia and
adjusting pH. Being cycled I only have to test nitrate at water changes
once a week and change out only 20% of the water. On occasion I'll run
the whole gambit of tests to make sure everything in on track, which it
always is. ;-)