Like you, I've had reasonable performance from Clevo/Sager for software development. One thing I would possibly look for: Get the _heaviest_ laptop you can find with them. Those typically have much more aggressive cooling systems than the lighter models. Case in point: Sager 9377s at XoticPC. If you go to the gallery and locate the view of the bottom of the laptop, you'll notice multiple intakes with extensive venting out the back. XoticPC in particular can do a copper cooling upgrade which might be worthwhile to evaluate. (Haven't tried it personally)
I'm mentioning XoticPC in particular because I've gotten 3 or 4 laptops through them and have been happy. They're pretty slow to ship for custom options (they don't keep a ton of custom parts in inventory), but I've been happy with the customized product.
Laptops will always be a bit of a problem due to small packaging/weight requirements, but perhaps these tweaks can help get you there.
Xotic PC has quite a few good laptops and a ton of customization options. I've purchased several laptops for myself, my wife, and my customers through them. The one big warning I would say about them is do NOT order them if you are in a hurry. They do take time to build and ship if you get customization options, and they don't seem to carry a large supply of their parts on hand. (Don't blame them for inventory tax $)
Other than that, they're always super friendly to deal with and I always get my laptop just the way I want it.
There is hardly a thing in the world that some man can not make a little worse and sell a little cheaper.