I think a normal sized (for your tank) powerhead would be plenty of extra current in addition to a filter. I would recommend another canister filter, as the bio-filtration on those is really un-comparable dollar for dollar. You might even look into making a home made canister, I have made countless filters throughout the years and all have worked just as good, if not better than any canister filter I have purchased retail.
All you need is a water tight container (for your tank id reccommend the container be able to hold at least 1 gallon, 3-5 would be ideal). After that just some pvc pipe, sealant, a water pump, and some hoses. Check out the DIY forum there are quite a few write ups that give a great perspective.
As far as media goes, I always just threw a couple inches of filter floss near the intake of the canister to take care of the mechanical side of filtration (clearing out debris from the water), and then the rest of the media is usually some sort of ceramic media to allow good bacteria growth. Anything with a high surface area will work. I recently stumbled upon a DIY thread where they used shower loofahs (the big mesh ball kind) and worked perfectly.
Good luck with the decision!