Hey Squawk, are you saying you can afford an Eheim 2224, but would rather take a chance on a Penn-Plax Cascade filter? At least we know Eheims are from Germany. Penn-Plax doesn't seem to want people to know where there filters are being made. I'm not saying that they are bad, but if you don't want to spend the money on an Eheim then I'd probably give both the Fluval and Rena lines before buying a Penn-Plax. I don't run undergravel filters so I can't comment there. As for a 300 watt heater on your 46g tank it kinda depends. If the night time ambient air temperature is something like 65f then that would be a good bet. If your house doesn't get below 72f or so then a smaller heater would work just as well. You may even want to consider using two 150 watt heaters instead.