I can compare the brand spanking new Garmin Edge 840 and the somewhat less spanky
Garmin Edge® 530 Bike Computer with Performance Insights
Garmin Edge 1040 vs 1030 Plus: Right Now I'd Buy THIS One - Sportive Cyclist
Garmin Edge 540 & 840 Comparison - Performance Bicycle
Garmin Edge 530 MTB Bundle - GPS Bike Computer Wireless Cycle Computer
Garmin Edge 1040 vs 840: Which Is Best (For You)? - Swiss Cycles
Garmin Edge 840 Cycling GPS In-Depth Review
Edge 1040 vs 840: You should buy THIS one
Garmin Edge 840 Solar GPS Cycling Computer (Black) - Performance Bicycle
Garmin Edge 1040 vs 840: Which Is Best (For You)? - Swiss Cycles
Garmin Edge 1040 vs 840: Which Is Best (For You)? - Swiss Cycles
Garmin Edge 840 Solar - GPS Bike Computer GPS Cycle Computer
Garmin Edge 1040 vs 840: Which Is Best (For You)? - Swiss Cycles