External Filter...

Hi all,
My wonderful wife bought me a year's subscription to Practical Fish Keeping for my birthday. It came with a free JBL e401 external filter. The question is, is it worth adding it to my Aquanano 40, which already has more than adequate filtration in my opinion. I haven't had any issues with ammonia or nitrite since setting up the aquarium. I do get a bit of debris floating around the tank, though this has dramatically reduced since I added more plants. Pros and cons of the external filter would be welcome.

P.S. I've already tried justifying the need to buy a new tank for my filter. This was met with a resounding 'no'.

Thanks Sue. Option 3 may be possible as I would still only have one tank. I may have to setup the new one before getting rid of the current one for the welfare of the current fish. Who knows how long the transition could take?!