I know this question, and the answer may be more complicated than yes or no, but in general, should a fluval 306 be adequate for a 40 gallon breeder?

I was originally going for the marineland 27 gallon cube (which based on their dimensions, is actually about 31 gallons) but I think I may upgrade to a 40 breeder, as the space it's going in will fit that tank BEAUTIFULLY!

The tank will be planted, and be fairly moderately stocked, I don't intend to overstock like crazy, but I am pretty sure the 306 has already been purchased for me as a gift, so I figure if it'll work I'll keep it, but if need be, I can take it back and upgrade to a 406.

What do you think?