Rayavadee looks too crowded, like a typical family resort.
Hardware also looks more like 4 stars? Water doesn't seem very clear, but might be ok.

Cempedak looks very nice! Any downsides to it? Seems like it might rain quite a bit in April? In all the videos on YouTube it was overcast or raining. Hmmm...

I've never stayed at an Aman before. Not sure if I want to since I'm afraid I'd never want to stay anywhere cheaper again.
Amanoi definitely looks very nice. Beach looks nicer than at Amanpuri.
The thing with both Amanoi and Amanpulo is simply that they are quite far from SIN. No, not terribly far away, but we'll be flying from ARN, so we will already have quite some time on the plane.
We then have 10 days on the ground in total, and I want at least 3-4 nights in SIN/KUL, leaving only 6-7 nights for something else. And then Amanpulo/Amanoi simply is quite far. I think it's better to go there on different trips.

I'm really torn on Amanpuri. After having read some more reviews, it sure looks nice. I just don't think I can make myself pay 1200$ per night or more for that. For that it just doesn't have the wow factor for me, judging by photos.
But like I said, I can imagine one would think otherwise after having stayed at an Aman.

And just to comment on [MENTION=231544]scented[/MENTION]'s reply: I was really trying to avoid that misunderstanding. I'm sorry I obviously failed. I am not looking for the best of the best. In fact, I'm a bit happy I haven't experienced it yet because I feel, it becomes harder and harder to go for less expensive options, the more you've seen. I'm just 32 years old, my girl-friend is 25. We still have time to do that later. Basically all I want is the level of service of a Conrad or St. Regis. Just give me the Conrad Koh Samui with a better beach and I'll be happy. I think we paid 280€ or so for a stunning pool villa at the Conrad Koh Samui (granted, we purchased points). I'm sure the service was far from what you'd get at an Aman, but it wasn't 3-star family hotel either. My girl-friend got sick and they couldn't have done a better job organizing an ambulance to the private hospital etc.
Yes, there was room for improvement (they didn't notice I had gone to the beach - I had to walk back and get a towel), but that was forgivable.
Also, the beach doesn't have to be perfect. Mr. Samui took us to a public beach with 2-3 star resorts on Koh Samui, and that was nice enough. Much better than what the Conrad had.

Cempedak really looks quite nice and it's easy enough to reach from SIN. The alternative would be to just go for Langkawi as planned - although we've been there before.