The X3440 fits nicely between an i5-750 and the i7-860. The X3440 might not be quite as easy to overclock as high because of the lower multiplier but I've seen ones running at 3.8 GHz without too much trouble.
Here's the Intel Xeon socket 1156 lineup:
That's running the default 19X multiplier but if you enable turbo mode you can also try using the 20X multiplier, full time.
It's Prime stable at this setting and the core voltage isn't too high yet so there's still room to play with it.
That's $40 more than a Core i5 750 at Newegg. $40 bucks doesn't buy you very much these days so $40 bucks for hyper threading and similar maximum overclocks doesn't sound like too bad a deal to me. You can impress your friends too when you tell them you're running a Xeon chip. There are no guarantees but traditionally the Xeon's have been better binned compared to the consumer level chips like an i5-750 so maybe you will be able to overclock with less voltage or it will be able to run at a higher temperature before losing stability. It's very unlikely this Xeon will be a lower grade chip so you have nothing to lose, except $40 I guess.
I'm using a generic case (purple sky island) and a Coolermaster 212plus in a push/pull.
This is the only 1156 I own right now. I have reduced the voltage to the cpu to 1.235v and currently running 60c at 100% load
just got my x3440 build put together! i'm running it in a gigabyte p55-ud4p. haven't had a single issue thus far. the system posted on the first try. just throwing this out there for anyone who's considering a lynnfield xeon but was wary of which mobo to drop it in.