Well done on the upgrade. unfortunately a lot of big plecos end up in tiny tanks.
have heard this about the AR980 filters, mine is silent though strangely enough.
if you go for a canister filter you may have to do a few minor modifications to the tank to fit in the pipes. being a 212L tank 700-1000LPH should be fine. its very hard to over a tank, it just turns into extra space normally. The tank will begin to cycle while cold, but since i prefer live fish cycles then a heater would be preferable (plus gets rid of the waiting) until then you'll need to be adding some form of ammonia to get the bacteria starting. easiest way is to add a small amount of food every day until your heater arrives, test your water for ammonia, nitrites and nitrates then add some of your fish. tbh just the 5 black neons would probably be too light a load for the ammonia to get to dangerous levels anyways.
btw what kind of gourami is it???, gold honey gourami = small species, Golden Gourami = needed a new tank as well.
if your worried about the driftwood tannins you could try boiling them, or just flick some activated carbon into your filter. they are normally harmless and personally I quite like the look of them in certain situations.