I got one of those back during Black Friday. It'd probably do the job for your 3-card rig. Just note that there are 3 lines of PCIe connectors, each with 2x 6(+2)-pin connectors, and both of the connectors are quite close at the end of each line. (Meaning you would need extenders if you wanted more flexibility with power.)

Count up the connectors on your cards and risers and think about it, knowing that you also have molex connections for risers. (Or SATA adapters, which are rated for less than 4-pin molex connectors.)