I dont have time to do a full spec like i have been doing for a lot of people on here over the last few days. But you seem to know what to do anyway.
Few pointers:
The abit Ip-e will not overclock and has bad bios rebooting problems so spend that bit more and get the Gigabtye mobo which will overclock well and is great for the price.
The seagate drives are incredibly fast but i beleive they are quite loud.
The benefits of going crucial balistix do not outway the cons, let me explain.
Geil 4x1gb is like 80 quid, same for OCz 4x1gb. They will both do up to 950mhz and are both a lot more reliable then crucial balstix where you could spend the rest of your lift RMAing them ever 3-5 months. The difference between 800mhz and 1000mhz with 2gb of ram in gameplay is nothing anyway! get 4gb of either ocz or geil for taht little bit more then the 2gb of crucial.
Get the OEM q6600 and get a turniq tower. these are amazing coolers and are only a few degrees behind the Thermalright, which i dont think are worth the extra cost as you may have to lap them as well due to their poor quality control. Also i would get some artic silver to stick it down with as i always like to use good thermal paste. no point spending money on a good cooler and going cheap on the paste that sticks it down.
If you can strech the extra for the Antec P182 case you will have a very nice case indeed. Quality build with sound proofing, including silicon pads to put hhds on so that the seagates will be quieter. Compartment for psu to keep the heat it produces away from the rest of the components a lot with a good design for air flow and 2 holes in the back for water cooling.
Furthermore i strongly suggest getting a GTS but wait to get the new ones. They will be getting mor streme processors and a smaller die so they will be overclocking monsters and pritty much as powerful as a GTX. The current GTS's already overclock to GTX speeds but lack the streme processors.
Hope taht has helped.