Re: E2180 vs E6550
The upside with the E6550, is the amount of L2 cache. It's 4MB vs. the E2180's 1MB. But I don't think it's much of a difference, unless you're using programs that are more dependent on cache.
I'd go with the E2180, because it's cheap, has a higher multiplier (so it's easier to overclock), and gives you the option of having to save more, for a better processor in the future. If you get the E2180 to around the 3.4-3.6GHz range, I think it will be equivalent to an E6550 at 3.2GHz, and the cache won't matter much at that point.
If you do want a little more cache than the E2180, and even a higher multiplier, check out the E4600 and E4700. They have 12x and 13x multipliers respectively, and both have 2MB of L2 cache.
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