I've decided to stick with the P5B-E onboard for a bit and then I can always buy a soundcard if I don't like.
The onboard of my Dell Dimension 4700 (family pc o_O) gives acceptable surround sound already so I expect the P5B-E sound to be no worse.
The memory I was trying to get just went out of stock, this means I'm looking for other memory, and I'm giving the DDR2-533 ones a chance now, as well. I'm not too keen on getting DDR2-800 memory, given the price and the marginal different with the 667.
This has shed another light on things, because the DDR2-533 memory should be more appropriate if I don't plan to overclock... The C2D FSB runs at 1066Mhz which is quadpumped from 266, so that would make it go well with 533 mem in dual channel for my memory to run 1:1.
But on the other hand, I will likely o/c the CPU (over time) and I could get DDR2-667 memory and up the FSB to 333Mhz * 7 = 2.331Ghz. This should be a little under what I've read it can handle, so that should be safe, but I don't know if the P5B-E motherboard can handle a FSB o/c to 333Mhz.
I see no other useful overclocking possibilities if I get the 533 RAM, but if anyone has a good rate, I'd like to hear it. I don't know if it's hard or even possible to unlock the multiplier on the E6300, which would enable me to fine tune the 533Mhz mem better. Or... maybe the DDR2-800 after all. The P5B mobo is capable of running cpu:mem at 4:5 so it would give more possibilities.
P.S.: suggestions for the best brand out of the following are welcome:
Buffalo, GEIL, Kingston HyperX, Kingston ValueRAM, MDT, OCZ.
P.S. 2: I could also get an E6400 for the higher multiplier (8x) and possibly save a few bucks by getting DDR2-533. I haven't looked into the stock and o/c ratio possibilities yet, though.