I understand why you want more power, but a port of Maemo/Mer/MeeGo won't be hitting an Android device anytime soon, realistically. I suspect Android devices are locked down to prevent this. And you should know, if it were to happen it won't be as optimized as the real deal (N900) so performance will really take a hit. But you should also know how much power difference their is between your likely candidates:

I found out on a few threads that the OMAP3530 (600MHz) is slower than the Snapdragon (1GHz), no suprise.

But what I also found was it was only marginally faster. Something listed as overclocking the OMAP to nearly 870MHz is equivalent to an underclocked 768MHz Snapdragon (eg Acer Liquid A1). They're both derivatives of ARM's Cortex A8 so no suprise.
Random Google searches, I found that the 3430 can do 1200*** MIP/sec (Millions of Instructions per Second), while the QSD8250 can do 2100. ***In addition, private benchmarkers point that the OMAP is slower (248, 433) than QSD (427, 674) MIPS for Compressing and Decompressing respectively.
However the QSD would obviously have an unfair advantage with double (256->512MB) RAM.***
In terms of CPU, upgrading from the N900 to a QSD device should yield you around 13-46%*** more power, which may or may not be necessary or even accessible for the Applications your running.


On a side note, I've read the QSD doesn't have true graphics accelaration ie a GPU. And this is no suprise, as HTC has been supporting QSD for a long-time and although processor speeds/performance grew (or multiplied) several times over time, the graphics capabilities have never increased substantially. This is because HTC did not buy/include the 3D drivers for their devices, so their was no hardware acceleration.

QSD's can average 22M polygons/sec a number very poor to such a powerful CPU.
The N900 has a dedicated GPU by PowerVr: the SGX530 which (is outdated now) can handle 14M polygons/sec.
Technically a small (30-50%) performance boost.

So, in terms of emulation, upgrading from the N900 to a QSD device should allow you to run much more fluidly with the 35%*** in CPU and 35% GPU power boost. However, as said before, the likelihood that "MaerGo" will be ported is low, let alone an optimized one.
So instead you'd be thinking just go with the Android OS that came with it. But also remember that native applications will always perform better than their "java" counterparts and this will be noticeable on "high-performance" Applications. The overall performance will be very similar (don't expect more than 15% benefit) between the N900 and the Android QSD devices.

Have a look at PSX emulation comparisons between the two platforms, and so you'll see the truth behind it.

Or even compare iPhone 3GS emulators to the QSD devices since the 3GS is also in the power range of the N900 and runs natively!

Glad to share some info to all of you

ed: sorry I can't spell!
*** ed2: I found other sources disproving the MIPS so I've corrected those claims, meaning QSD performs a little better than previously stated but doesn't alter the lasting conclusion/comments.
Those sources are 3GS vs Nexus1 and Private benchmark that confirms the other source for the power difference