Eheim Aquaball?

I have a 10-12 gallon octagonal tank with a single sheet glass cover with a cutout section only a few inches long to fit all cords, hoses, filters etc through. I have a sponge filter for it, as one of it's uses is for fry, but I am not real happy with that filter because it tends to separate top and bottom and it is driven by an air pump which is very noisy.

So I am looking to get a new filter for it, but there is only a small amount of room on the opening so many of the HOB filters would not fit. I was considering an Eheim 2213 but it might be overkill. I might turn it into a betta tank and they aren't found in river rapids usually!

So now I am looking at an Eheim Aquaball internal filter. I am not familiar with it but it sounds good from what I have read. Is anyone familiar with this filter? Anyone have any bright ideas for what filter I could use that would be an improvement?

The Eheim I am looking at is Aquaball 2208 reccomended for tanks 30-60 litres, thats 8-15 US gallons and I can buy it for AUS $75. The Eheim distributor in Australia has decided to get seriously competitive on price and make his money on volume sales, so the prices have come way down here.

http://www.eheimasiapacific.com/prod_int_aquaball.html

I've looked at a few of the smaller filters. They all seem a bit cheap and nasty to me. A lot of them take cartridges which will keep on costing you. The little sponge filter I have together with the pump cost over $50 already and it would like me to replace its cartridges every 6 weeks for $5.00 a crack. So I am looking for something more reliable that takes substrate and runs quietly.

I'm interested in this Eheim because the company has such a good reputation. I am very happy with the Eheim 2215 on my 50 gal tank. I am curious as to what people who have used the Eheim Powerball think.

The little powerhead looks like it might fit on the tank but then I'd need to buy the filter to go with it. I also don't recall seeing that brand in Australia.