should I get a e8400 or a q6600

is there a speed difference, and would the fsb change anything e8400 = 1333, q6600 = 1066.

and does the l2 cache change anything. e8400 = 6mb, while the q6600 has 2x4mb.

they are the same price at my local store $199. 

(this for my second system.) 

What are you going to be using your computer for?

as a back up, such as when my main comp goes down(which is often) I want to use this for everthing, app, games and school

If you're doing heavy threaded applications such as photoshop - rendering - etc then pick the q6600 or if you're a huge Supreme commander type strategy fanatic. But if you're not then pick the 8400.

I've been debating the same thing.

http://www.tomshardware.com/forum/248327-28-overclocked-q6600-e8400-compared-benchmarks-included

This should help some.

FSB is the most important part of the processer and in my opinion the entire damned computer. I don't care what else yu got in there if the FSB is insufficient the damn thing will always be a snail. I run my CPU at 200MHz(not a typo) and it can run all my programs at the same time and not skip a beat. Why integrated FSB man. Its what its all about. One is offering yu higher for the same price, take it.

what Squalliam said.
Unless you're into heavy photoshopping, video editing, encoding, programs that take advantage of 4 cores, otherwise a dualcore E8400 would be more than enough.
for games the E8400 would be a better choice too.

I'm in the same boat and am leaning towards the quad because it's more flexible and more future-proof (granted, this is more applicable if you plan to stick with the same proc for 2+ years), plus the differences, gaming-wise, are mostly negligible.