The XP3 is an excellent filter with plenty of room for customizable filteration media that you can adjust for your needs. Never undersize your filter as it'll cause issues in the long run and you'll eventually end up upgrading in the end. The Rena Filstar xp line are known to be the best for cost in the canister filters. Some will recommend an eheim, but they definately don't qualify as cheap
I know you asked about filteration, but i'll come right out and say it, Use the stocking calculator before buying your fish. Once you know your filter and tank size, it'll tell you just how many fish you can stock your tank with. it is stickied in the freshwater section.
I'll also strongly advise against impulse buys for fish, go to the store, look at the fish there, and decide which types you'll want, then go home and look to see if they are compatible with the type of tank you want.