I have left the alphabetical sequence and turned to my first DC project: Seti@Home.

What CPU to use for Seti, and why? Now that's a question not as easily answered as with pure-CPU projects.
The stats at the Seti-website show that the top-computers are heavily foreseen from dual-core GPUs and, for what's it worth, foreseen from 64-bit Windows versions.
Problem is that the Seti-scores for those systems are highly influenced by their GPU-scores as regarded to the total scores of a given system.
Also, for what's it worth, there is a special Top GPU models ranking list, but that seems to have lost contact with the actually running models in the before mentioned top-5. GeForce GTX 570 is king of the hill in that list, and GTX-580, 590 and 680s are not even mentioned....right, at best these are all-time scores and they are definitely not the recent average credit.
Note the Bulldozer FX-8150, as first AMD CPU, combined with four GTX-590s (two GTX-590 with two GPUs each of course) at #7 of the Recent Average Credit scores.
All-time scores are headed by a Phenom II X4 920, combined with an astonishing 8(!) GTX 295 GPUs, which translates as 4 actual GTX 295, each with two GPUs. Could not imagine a mobo with eight PCIe slots myself, but who knows?

So for more 'clean' stats we have to rely on WuProp, that also might give insight in which GPU gives the best results.
Seti itself sees four different applications, whereas WuProp sees sixteen -and does not even count Seti@home v7 amongst them-, but I'll give it a try.

Astropulse v505 aka astropulse_v505
A dissapointing low number of CPUs were in the WuProp database for this application. As the results stand, it seems to be that the i7 with its 8 or 12 hyperthreaded cores gives the best results per CPU per day, but there is an almost total lack of AMD CPUs to compare them with, and not much Intel data either.

Astropulse v6 aka astropulse_v6
Apart from that sole model i7 that outruns the pack with a factor of 100 the results look good. Best AMD CPU in scores both per core as per cpu per day seems to be the six-core FX-6100 (20 to 30% OCd), followed closely by the Phenom II X6 1100 and the Bulldozer FX-8150, while the best performing Intel core was that of the Core 2 Duo Mobile T6400. Best Intel CPU however was the Intel Core i7-970, thanks to its 12 hyperthreaded cores.
Note that you can buy three FX-6100s for the price of a i7-970, and that three FX-6100s will outperform a i7-970 by a factor of 2. You'd need 3 PSUs to go with the three FX-6100s of course, but I take it that the point is made clear.

Astropulse-GPU client
There is not much to compare with each other, as there is at the moment just one nVidia card with data, the GTX 550Ti. That takes 96 minutes to complete a WU, while the best Ati/AMD card in the data -the HD 6970- takes 33 minutes. But let's wait for data for the GTX 590 before we jump to conclusions

Seti@home Enhanced aka setiathome_enhanced
The 8-core Bulldozers may not have the top-scores per core for AMD (though they come pretty close), the fact that you can multiply that score with eight makes them the best AMD cpus for this application. With a daily score of 5k to 8k credits they can hold their own against the i5-2500/2500K, but have to bow for the i7-2600/2600K, the two best performing Intel consumer chips.
The per core score of the relatively cheap (just had a price cut bring it under $100) AMD Llano A8-3870K surprises in a positive way (Who does not remember the Llano reviews complaining about an old and underperforming cpu coupled with good graphics?) Insanely good results have been reported for the 24 hyperthreaded cores of the Intel Xeon X5650, but who can afford such a beast?

Seti@home enhanced GPU clients
In general the higher Fermi models score better, but a card as the Radeon HD 5770 holds its own against the far more expensive (both purchase and 24/7 running) nVidia models and completes a WU in a mere 5.4 minutes.