I'd change your board if I was you. Try the EVGA 680i board.
There are a lot of memory compatibility issues with the P5N32 where it won't recognise 4 sticks of ram in it.
There are very few sticks that it supports and even then the listing changes regularly. There are no such issues with the EVGA board.
I ended up having to buy 2x2Ggig kits as this was the only way of getting the board to read 4 gigs.
Plus for overclocking purposes people cannot get higher than 350mhz on the FSB with quad-cores with the Asus board. Again no such issues with the EVGA board.
I am in a quandry, I am a gamer however I like to do stuff like photoshop, listen to MP3's, encode video for my 360 and iPod. Would the Q6600 be a better choice for a CPU over the E6850?
Would I get a major difference in gaming performance by comparison or does the fact I am leaping from a 1.3ghz T-Bird make the difference negligable?
Is Crysis a game that uses all 4 cpu's?
How is the Z-550 compared to the Klipsch Pro-Media 5.1's in terms of sound quality?
What's the benefits of SLI?
The Q6600 will be better than the E6850 in Crysis and most future games and video encoding. The E6850 will do better in Photoshop (yeah, I know it's surprising, but it has been measured) and in most current games.
The difference will be negligible, except maybe in video encoding where the Q6600 will win by a noticeable margin, assuming you have software that can use all 4 cores. Differences in games will not be very noticeable because cores 3 and 4 will not be used anywhere near 100% even in games that do know how to use them. Supreme Commander for example does use cores 3 and 4 but only at around 10% each. That's because in a game you don't have 4 tasks of equal difficulty to do in parallel, you just delegate whatever you can to the spare cores.
I would expect Klipsch to be better (at twice the price), but Logitech makes great stuff too. I would rather pay 300 for the Z-5500 than 600 for the Klipsch, even if the Klipsch is better, because my ears won't really notice the difference. If this is an important thing for you I suggest going to a store and listening to both, then decide. I did that and they both sounded fantastic.
SLI has very few benefits, the disadvantages are much more important IMO. Do consider SLI if your screen resolution is 2560x1600, otherwise a single 8800 GTX is a much smarter idea.