My curiosity was piqued by your comment that the Master Class are 4x the volume versus the Genelec G One so I did some simple comparisons.
Dimensions for MasterClass 2504 (LxWxH): 8.15 x 5.71 x 9.06 inches
Dimensions for G One (LxWxH): 7.69 x 4.75 x 4.5 inches
If we only consider volume, the MasterClass 2504 is 2.5x larger than the G One. There is no denying that the G One is one compact speaker but the MasterClass 2504 is by no means a large speaker ~ its footprint is fractionally wider than an 8.5x11 inch piece of paper folded in half and at 9 inches tall, it's the same height as the Creative Gigaworks T20 which is known as being a compact yet good 2.0 speaker system. If we compare the footprints (LxW) of the G One and the MasterClass, we see that the MasterClass 2504 is only needs ~27% more space.
Unless there was a strict vertical constraint, I don't think 5 inches or 9 inches matters all that much. If we start considering manufacturer recommendations for placement, these differences in physical dimensions start to matter even less ~ Both Genelec and CEntrance recommend using a stand of some kind to elevate the speakers above the plane of the desk and leaving several inches of space around the speakers for best sound. Also, while I haven't compared these two speakers side by side, I would imagine that the G One's rear-firing bass port would need more room behind the speaker than the MasterClass 2504's front-firing port.
Hmm. It's kind of funny ~ I initially mentioned the MasterClass 2504's because there were offered here on MassDrop, but after typing this up, I might have convinced myself to get a pair.