I don't know these 2 filters but take it the numbers refer to GPH,,if thats the case, go with your ac 300 and a fluval 304,,that is a total of 604 GPH which is near enough to the ten times turnover recommended, plus with a cannister (304) you can get away with slightly less turnover as they are very efficient.
No point spending hard earned cash, when you have a perfectly good filter already that just needs topped up.
Well thats my two bobs worth.