NP9280/D900F - Best Value CPUs, Power vs. Dollar?

I've been shopping around for what would be the best processor to install in a working D900F laptop. I'm getting a working NP9280 soon, and I'm wondering what's the absolute best processor that will work, and give me the most raw power for my money.

I recently discovered that the W3570 Xeon, a Quad-Core with HT running at 3.2 GHz(to compare, the i7-920 runs at 2.66 GHz), was going for $90-$150 for used on ebay, which is about the same value as the i7-920. Granted, it's a Xeon, not an i7, but you do get much more CPU headroom regardless.

Another value piece is the E5540, an 80W processor(compared to the i7-920 and W3570's 130W rating), that has 4 cores and HT. Could be called a frugal i7. Goes for even less than the W3570.

There are sketchy Engineering samples all over ebay, I generally avoid those. Those things were made to be tested, whereas the final versions of the Xeons were made to run forever.

I understand i7s are more suitable for gaming and standard PC use, but I run Folding@Home and do a lot of Video Editing, so I tend to like Xeon-powered machines more. I also appreciate the stunningly limitless reliability, and I believe they stand up better to high temperatures. Plus, it's not everyday you get to tell your fellow PC enthusiast that you have a Xeon-powered laptop.