yeah, that is overdoing things.
for $1.5K-1.8k, for the sole purpose of gaming alone (if the forum category is any indication), you could get yourself a Haswell + 780ti. that should last you 3-5 years, before you get another $1.5k-1.8k PC that'll outperform it and lasts you another 3-5 years. for up to $3.6K (let's say $3.2K, if you manage to sell off the first PC for cheap), you got two powerful PCs in the span of well over 7 years, vs a single near $6K PC that'll likely be outperformed by a $1.3K PC in 3-5 years time. case in point; the nehalem CPU vs Sandy Bridge:
http://www.anandtech.com/bench/product/45?vs=287 . to re-iterate a $999 at launched nehalem CPU in 2008 just got beaten by a $300+ CPU in 2011. the jump from SB to Haswell didn't result in much, but 4-5 years is plenty of time for a new microarchitecture to outperform and impress us.
future proofing just doesn't exist, at least not one that's financially viable. and as Benevolence mentioned, as cool as a custom water cooled rig is, the amount of maintenance and long term costs to do so just isn't for everyone.