Way overkill! The Eheim run hot and you could run a single 300 watt which is rated for 265g which I do believe it could handle. This would be cheaper than 3 standard 300 watt heaters. Or if you are one of the just in case for redundancy sake people, two 200 watt Eheims would probably work just fine.
On my 120g I have one 300 watt Eheim and I had to turn it WAY down because it was more heater than was necessary. I believe I could have used the 200 watt model and been just fine. Previous to this I has two Hydor ETH inline 300 watt heaters on this tank and realized it needed only one. I pulled the two Hydors for my 210g and I'm sure it is more than enough. But this of course depends on the location of your tank and the temperature variances there.