I have a pair of Yamaha HS50Ms. This would be generally comparable to the updated Yamaha HS5. I wonder why the HS5 was not on your list. The newer speakers have improved frequency response vs. the HS50M

Maybe the HS7 was a play to prevent from getting a sub - but I have the 5 without a subwoofer and find it fine for the keyboard (yes, a sub would be "better" but HS50M alone is adequate for my purposes). Perhaps if you're doing other work you'll want to go for the 7's for the improved bass response.

Hello Jason - no reason not to include Yamaha HS5s - I favour the KRK Rokits though, because they offer RCA inputs, and all else technically seems on a level. My mixer has RCA outputs - although I am thinking not so much connecting the mixer output to the speakers, as to plug the Rokits into the Tyros in place of the existing satellite MS202s - this would leave the sub-woofer in place, but I wonder about the cross-overs being compatible. But it is an option, and should greatly improve the mid-range (C3 to C4 especially), which is the area the Montage gives me trouble. Not the Korg, nor the Tyros - just the Montage.

I will take another look at the HS5s though ...

You mentioned the size of the HS7 as a downside - so the HS5 is my suggestion to place size on a level playing field.

With monitors, there is no wrong answer and ultimately it comes down to your ears. I prefer a true sound without too much color and also have some solace that the keyboard has been tested primarily with Yamaha sound reinforcement (not to say they do not test with other reference speakers). The KRK has some bass color added (not exactly proper terms, but I think in terms of color) which may appeal to your ears and also help make up for the lack of a sub even when using their smallest dimension offering. I had previewed an S90XS which was connected to HS50M (or maybe the 80M) and decided to go with that series of monitors as I was happy with the piano sounds which I felt, for what I was doing at the time, were most sensitive to getting the monitors to match the board.

But also keep in mind my opinion on the sound doesn't count for anything other than for my own personal use. Assuming you've narrowed the options down to a short list - it would be best to hear those in your studio before final purchase. The room colors the sound. This is not always practical - so at least hearing them in person in an environment without too much acoustic distraction would be 2nd best. For the most part, these are near-field directional monitors - so the first wave (non-reflected) is going to dominate. Angle the speakers so each is pointing at you and tweeter at ear level (height). You'll have a bit more flexibility with placement/direction of the monitors vs. the Tyros speakers - which is a good thing.

Although Rod mentions using RCA for his current mixer output - which matches the iLoud - the iLoud's lack of a balanced input is one spec which is of some concern. An XLR or balanced TRS connection will give greater noise immunity in the cable due to differential signaling. If the mixer had XLR or balanced TRS outputs - I would suggest using these over the RCA. If not possible, perhaps purchasing a converter or RCA-to-XLR cable would be a bridge. Such a converter would defeat the benefits of the balanced connection for noise immunity - but would be cheaper than replacing the mixer which, if only has RCA outputs, really should be replaced at some point to reduce it as a source of noise / coloring within the signal chain.

I have not heard the iLoud - the marketing information seems to focus on portability and associated pictures with a laptop and inclusion of an 1/8" stereo plug (3.2mm) which is for plugging into a laptop gives somewhat of an idea for the target usage. The frequency response listed seems OK. I would advise previewing these if at all possible at a store that carries Montage. I see availability of these speakers on 11/28 at such a store (although unclear if this is for online purchases vs. in-store).