If your reason for wanting another unit is based solely upon your RM1000 being "overkill" but it works fine otherwise, your reasoning may be flawed.."Overkill", of itself, is not neccessarily a bad thing.
 
Q: Is there such a thing as "too much power"? (JonnyGURU, #1 in who's who of PSU testing and reviews)
 
A: Generally, no. A power supply only puts out as much power as needed by the system's components. In some cases, an 800W power supply may actually use less power from the wall than a 500W power supply, depending on the efficiency of the units. Often times, buying an "oversized" PSU is a good choice due to it's ability to perform even under higher temperatures, a quieter fan because the unit is delivering a lower percentage of it's total capability and considerable system upgradability without having to worry about having enough power when upgrading a graphics card, adding a graphics card for SLI or additional hard drives.
 
You may be less happy with a smaller unit that may be more noisey, run hotter and is less efficient overall.