Well what sort of performance are you looking to get out of it? Personally, I remember 4 years ago when I got my dell i6000d and pinmodded from 1.5 to 2.0. Back then, that made a computer that was real worthy. It kept pace fairly decently with my desktop of the time, a p4 2.4c @ 3.2. A little slower, but completely acceptable for a notebook, and I had no qualms with using the laptop.
Fast forward to nowadays. I've got a e6400 2.13 @ 3.2 or 3.6. The dothan 2.0 just doesn't come close. I mean it's still fine mostly, but my usage patterns have shifted upwards, and I didn't want to have to adjust to being able to use the dothan. I usually run in excess of 50 firefox tabs, and the dothan just couldn't pull it off with the agility of my desktop.
But the t2370 (core2duo more or less, with 1mb of l2 cache) at just 1.73ghz handles what I need out of a laptop. I'm limited by the gpu, so gaming is a little out of the question, but that's fine since I don't need to be gaming on the road anyway. And at home, the difference between the laptop and desktop is really just mobility. I wouldn't be gaming in my bed anyway..
If you're fixated on overclocking, then the amd's with nforce chipsets (or is it amd? I haven't done much research at all in the world of the turions since in my opinion, they're a joke) should be able to clock to 2.1-2.3ghz fairly easily from the brief few threads I poked my head in.
Yonah, merom, etc, when used on an intel chipset, seems to exhibit a multiplier lockdown at 6x, so even at 200fsb, you'd be stuck with 1.2ghz, which in pretty much all cases of pinmodding, will yield you a lower clock yet. Unless you have a comparable cpu speed to start, and you'd possibly see benefits of going from 133fsb (well, 533 quad pumped) to 800 quad pumped..
That said, if you do get a laptop with a merom that also has an ati chipset, you'll most likely be able to overclock and still keep the multiplier intact. And if you can't climb from 133 to 200 via clockgen alone, you can indeed bsel mod on those. And from what I've seen, people are able to goto 240fsb even, and maybe higher (probably more likely if you adjust bsel to start from 200fsb if there are any strap differences that come into play).
So say you had the same t2370, which is 13x133=1733 natively. at 200fsb, that'd be 13x200=2600. You'd most probably be able to do this with stock vid. And if you were to brave 240fsb successfully, you'd see 13x240=3120. Hmm.. definitely possible with stock vid, but it'd start to become a gamble at that point.
At 3.1ghz, you'd definitely have in your hands a completely worthy desktop replacement! Although depending on what ati offers, you may be stuck with the ati igp. That is of course unless there are laptops with the ati chipset and dedicated graphics.
Hope this gets your balls rollin
Here we go!
That said, if you're convinced on a dothan, make sure the chipset is 915 and not 855. 855's only support 100fsb, and afaik, the pci/agp wasn't locked down, so if you were to go the clockgen route, you wouldn't get far.
However, all that said, there are a ton of $399 laptops nowadays, and depending on how cheap you can get that m65/d820 (sorry I didn't research what chipsets they are), it may be worth it to just go for a new $399 laptop. Compared to dothan, I'm sure turion is better.