None. Powerfull and Quiet do not mix - Powerfull emits lots of heat which means lots of cooling. Lots of small cooling = lots of airflow = noise, as sad as it is. The best options are: * Get a low power laptop, use RDP to a powerfull workstation / server. Alternatively: * Wait a little - the Ivy Bridge are now pouring into the laptops. As they are twice as efficient as Sandy Bridge (half power usage, about)... which means less heat to move and less power usage (less drain on batteries). The WIndows 8 "Generation" of hardware will be a big push coming in Q3 / Q4 this year. I am not saying "Windows 8" but with the Windows 8 focus everyone is aligning new hardware releases, and this time they have a really good BIG step forward lined up. On another note - depending how you define "Powerfull" the AlienWare machines are about he most powerfull as laptop you can get. You pay a steep price though... Price, Battery Range and - under load - NOISE.
I'd suggest SSHD (solid state hard drive) I have an ASUS SSHD and very quiet. You will pay a premium for this. Advantages is quick boot up, low heat, low noise, robust. I have 3 x ASUS laptops now but only one of them is SSHD. I wanted all to be that way but they are not easy to find and I was in a hurry to buy so the other two are conventional HDD. Many shops won't stock SSHD because of the price premium.
SSHD? First time I hear that. Everyone else (likely also the shop) uses he acronym SSD. This is right - they rock. Replacing all boot devices with them over time now (or moving storage to a SAN). But a good SSD is VERY good for a laptop. * Less power use. * Faster. Laptop HD are slow due to shock resistance. * No spinup time / power cost
Dell Small Business Vostro Ships Fast i3 or i5 with lots of RAM. I have one and can't hear it. Great machine. Don't fall for the i7. Look at the clock speeds on the i3 and i5. Less power consumption, less heat, less noise.
Lenovo X220 Tablet It's a very quiet laptop. I run XTRADER, CQG IC, a "bulky" excel model and a client/server application which interfaces with a CME colocated server. Battery life is my only complaint.