so, in essence what you want is a pc to last 7-9 years?
what do you expect of the pc in its latter years?
let me put it this way: my first homebuilt pc was built about 10 years ago and was around the same tier as the one you are building. high end but not bleeding edge. i'll list a few of the specs below..
amd3500+ 2.2ghz single core
2gb ram
60gb hdd 7200rpm
7800gtx
now, think about what you can do on such a pc today. i can play older games of the 90's, surf the web, use office programs and even cad or graphics programs albiet at a slower pace. dont even think about running any new games on it even on ultra low settings as it wont work.
pc hardware, especially when used for gaming, is short lived. at most expect 5 years of solid performance out of a system, after that and you will be having trouble. you can make small upgades to speed it up but in the end doing a total overhaul once every 5 years or so will give you the most bang for your buck. even if you bought bleeding edge technology you will not do much better.
i7 might buy you a little more time but its not easy to quantify. remember that overclocking is harder on your components and increases the risk of parts failing. the higher you overclock the greater the risk.
remember not all fans are push (inlet) oriented. are you sure that one fan is not in a pull configuration (outlet) and that the vent is really an inlet?
as far as stock fans being quite audible...it depends. the loudest fans in any system are most always the northbridge fan and the video card fan. the cpu cooler fan not so much. if you have good case airflow then the northbridge fan and the video card fan do not have to spool up to maximums. the larger the case, the less airflow you need. small cases heat up pretty fast so you want to exhaust all of that air.
also you seem to forget one key point: you need good fans for a watercooling setup. fans mean noise. also remember that the water pump generates a constant low humming noise. unless you have a watercooled northbridge and video card you will still suffer from those fans when your system gets hot and you will have spent quite a bit of money doing it. if you want silent you will want to watercool as much as possible and just have some ambient airflow in the case for parts not covered.
as far as what you would need...
for an i7 system with a decent video card you will need at least a 4x120mm, preferably 5x120mm radiator equivalent. a 2x140 super dense and wide radiator might barely be able to handle this. more than likely this would not quite be enough. you would also need a pump, hose, fill port if not a reservoir which is highly suggested and then the actual coolers. you might be able to fit everything in there but you will most likely end up mounting things by drilling into the case and mounting to the top. you might also end up having to drill a few fan holes into the top of the case as well depending on what the radiator can handle.
if you spend the time researching, buy quality watercooling components, and spend the time making everything right it can turn out very well. however, you will still have spent quite a bit of money that did not need to be spent for your purposes.
this extra cash you saved could then be used to upgrade your system in the future. watercooling and overclocking might make your system stand up to time a little longer, but not enough to warrant the extra cost.
about the trays.... you would have to ask lian-li about that.