I use 1.41v in the BIOS to get to 3.15Ghz. I would like to get 3.4 But to boot at that seems like i need A LOT more vcore, and that will only just boot in then blue screen or reset.
What is VID of your E4300? i.e the core voltage at stock speed of 1.8GHz? Coretemp can display this value accurately provided you have disabled C1E and EIST in bios. From this we can deduce how far you have pushed bios vcore of 1.41v for 3.15GHz from vcore at 1.8GHz.
Seems your E4300 is aleady at 75% overclock: [(3.15-1.8)/1.8] x 100 = 75%
Now 75% is a very impressive figure already and if you decide to push it to 3.4GHz then it will be 89%!!

. You will most probably need more vcore in bios to stabilise the cpu at 3.4Ghz.
I don't have any experience with E4300 but Core 2 Duo E6600 and Q6600 usually clock easily to 3.2-3.4GHz as their stock speed is set at 2.4GHz. In your case it may be more difficult to achieve 3.4GHz but give it a go.
When you say put the memory at 400, do you mean lock it to 400Mhz or just the ratio of 1:1 (if that's possible?)
Yeah if you can keep it at 400MHz (800MHz DDR2) then do so otherwise ratio of 1:1 will also be fine as you need FSB of 378MHz: 378x 9 = 3402MHz=3.4GHz.
I don't have much knowledge of Asus mobo as I have a Gigabyte mobo but have read through this article. I presume the article talks about the same mobo that you have:
http://www.anandtech.com/show/2427/1
The 3rd page talks about bootstrap and memory ratios. Apparently you should choose 'FSB Strap to North Bridge' as 400MHz. This will be more on par with your FSB of of 378MHz as this value is approaching closer to 400MHz.
With 400MHz strap, you will get either 1:1 or 3:4 as your ratios. Apparently (article has 3:4 other way round as 4:3) but 3 still corresponds to your FSB and 4 is for your ram. If you select 1:1 then your ram speed will also be 378MHz or 756MHz DDr2 and this is what you need.
If you choose 3:4 then your ram will be (4/3)x378=504MHz or 1008MHZ DDR2 which you don't want. Also you may need to up the northbridge voltage aswell in bios for stability.
It may seems complicated as to what I have written

but with that article and you having more experience and knowledge with your mobo and cpu you will hopefully be able to make more sense out of it. Obviously fellow overclockers opinion will be needed aswell especilly those who have E4300 or your mobo to help you with the process

.