The prices appear as quoted when I click on them. You are in the U.S. right? Newegg.com only ships to U.S. customers and if you are in another country, say, Canada, you may be being redirected.
1. Unless you are really confident in your abilities, don't do water cooling. It's expensive and if something goes wrong, your whole system is toast. Air cooling is very good especially when you consider that, for a computer, room temp is considered very cool. I go with the safer option of air cooling. If you're worried about noise, you can get special fans or material to put inside the case.
2. As for the six-core CPU's, that requires more explaining. First, whomever told you that should have mentioned that core utilization is largely determined by the programs. Second, not all programs will utilize two, four, or six cores depending on how they are coded, hence my "If you're going to be doing some higher performance video editing work which loves even more cores" part when explaining CPU's. Third, with gaming, four cores are just now starting to be harnessed, six core CPU's are still rare and the programs that use them typically involve rendering, data manipulation, or scientific operations. In the future, six cores will be more common and more used.
3. I very much loathe marketing departments... Intel's Core i5, compete's directly with AMD's Phenom II lineup to the point where performance differences are minor in real-world situations. Intel's Core i7 is another beast entirely especially at the i7 950 levels (Which cost about $200 more than the six-core CPU I listed above). Intel will be replacing the LGA 1366 socket, the one which runs the high-end i7 CPU's, with socket LGA 2011 which is not backwards compatible. This will effectively bring your upgrade options to a halt since you would need to replace your motherboard to use the LGA 2011 CPU's. In AMD's case, their upcoming socket, AM3r2, is pin-for-pin identical to the current AM3 socket, which makes backwards compatibility an option. Intel goes through sockets constantly and few are backwards compatible.
4. That is a standard ATX motherboard. Cases come in Micro, Mid, or Full ATX, however, motherboards come in Micro ATX and ATX. Many full and mid ATX cases support Micro-ATX motherboards and they all support standard ATX motherboards. Some full-ATX cases even take E-ATX but that type of motherboard is rare.
5. Use caution when picking out cases as shipping can be astronomical. Cases which have side windows or vents will tend to be louder. My favorite case is the COOLER MASTER COSMOS 1000 RC-1000-KSN1-GP
6. As for monitors, I like these: ASUS MS Series MS228H Black / Blue 21.5" 2ms(GTG) HDMI Widescreen LED
, ASUS MS238H Glossy Black 23" 2ms Ring stand & Ergo-fit LED
, and Acer S243HLbmii White 24" 2ms(GTG) Full HD LED
. I like LED backlit monitors for their energy savings, high contrast, and fast refresh rates.