i think that everyone is going to tell you the same thing, external is better.
a fluval 4 internal would run 180lts with no problems, cost around $90.00
a jebeo as wok said, for the price are a great filter, cost $140.00
http://www.deepblueaquarium.co.nz/filter.htm
for the $50.00 you get 4 x more filter.
i have them both and they are great filters but IMHO i would go for the canister, its a lot less work as you only need to clean it out every 6 months and later on add a small internal and the canister can be left 12 months. the internal also adds to the current.
but as it goes with most of us, the budget will decide