I've decided to go for the P5K deluxe, simply because it's had great write ups. One of which you'll find from respected member Clunk (search for it on here, definitly worth a read). The reason i'm going for it is that it offers exceptional overclocking potential.
I guess you should ask yourself, are you going to be overclocking? If you are then yeah stick with the P5K.
Secondly, the debate over an E6570 or a Q6600 is a tricky one. Im going for the Q6600 because I'm going to be doing a fair bit of Photoshop work (im a graphic designer/web dev) so it could utilise the extra cores i've been told. If its simply gaming then the E6570 should be a bit better for your needs. But match the quad core with the P5k and you'll get some impressive results that should leave the dual core standing after a good overclock.
To overclock you'll also need decent cooling, i'm not familiar with the Zalman but after lots of reading and research can recommend the Scythe Infinity, Tuniq Tower and Tt Ultra 120 (all for around £30-£35). These are top of the range air cooling parts so you'll be covered in that area. But if you do decide you're going to be overclocking, you'll need to look at watercooling to do so with stable results.
The RAM, i'd stick with 800Mhz stuff for your needs. I don't think you'll benefit from the faster stuff - but someone else should be able to advise you better hopefully on that one.
PSU - seems fine. Remember, never get the cheapest own brand stuff with a PSU!
Optical drive
imo is an optical drive
The case, i've had the P182 as a front runner for my own system Im building next week and it looks an Excellent case both in design, and build quality. It's really got the system builder in mind.
Sound - not being much of an audiophile, I usually stick with my aging Soundblaster 5.1 Live or the onboard jobby - not sure of what kind of impact this has on general performance but I cant imagine much. Its all relative to the kind of speakers you have so I guess only you can know whether this is good enough/overkill.
The motherboard should come with the SATA cable so scrap the extra purcahse and buy me a beer
Just remember, take your time with it, read as much as you can so you're making as informed a decision as you can possibly make. After all it's your hard earned cash you'll be spending and you'll no doubt be using the computer for a year or so at least.