Idle temps are irrelevant . The design of your loop should be based upon stress testing. 29C is "room temperature" this time of year (nothern hemisphere)
As far as all-in-ones ... what kind ?
CLC (Closed Loop) - like your H100i.
Noise - Huge
Cooling - Comparable to the betterair coolers
Reservoir - No
Copper rads - No
Mixed metals (source of galvanic corrosion) - Yes
Expandable - No
Pump - 0.11 gpm, low head
OLC (Open Loop) - Swiftech H240-X
Noise - Moderate
Cooling - Better than CLCs and air coolers
Reservoir - Yes
Copper rads - Yes
Mixed metals (source of galvanic corrosion) - No
Expandable - Yes
Pump 1.0 + gpm / High head
As a mid step, I'd suggest a Swiftech H240-X. Just did two of these in Phanteks white Enthoo Luxe cases and they came out gorgeous. None of the problems of CLCs... you can start off as a swap for your H100i and save 7C off your overclocked temps while cutting noise by more than 75%
http://www.hitechlegion.com/reviews/cooling/liquid/42047-swiftech-h240-x-open-loop-280mm-cpu-cooler-review?showall=&start=3
You can also expand the loop down the road, by adding water blocks for your GFX cards, MoBo, whatever, add more rads ... the pump is capable of these additions.
It performs as well as a custom water loop because that's basically what it is .... they took 3 popular and highly regarded custom water cooling components and pre-assembled them at the factory.
http://www.swiftech.com/H240-X.aspx
This allows you to work your way up gradually in both money as well as your own comfort level as to what you want to tackle.
I love custom water cooling ... not for performance as the benefits just aren't there anymore with today's highly efficient CPUs / GPUs, but for noise reduction and aesthetics.