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Yes that makes sense - thanks for the information and suggestions.
I'm pretty sure I can do it a number of ways - I'm trying to minimize the amount of equipment that will need to be purchased while maximizing the efficiency of the system.
I think the biggest decision I need to make, or at least one of the options, is whether or not I want to keep the furnace in the equation. If I keep if, auxilliary heat is taken care of, but it saddles me with a non-variable speed motor (could be swapped for a retrofit, but that's not the same) and a split geo unit (which I think excludes the Synergy). That makes the forced air side of things pretty simple, but leave the hydronic problem unsolved.
For the Hydronic I'm considering (1) Synergy3D or equivalent dual capable unit (2) Water to Water Geothermal (3) condensing wall hung boiler (4) High efficiency water heater.
I suspect something like the Triangle Tube smart multi energy tank might place a key role in allowing a tie-in between domestic hot water production and space heating.
The controls side becomes a whole 'nother problem to solve. There will be 2 forced air zones which have overlap on the 4 hydronic heat only zones. I certainly see where two pieces of equipment greatly simplify that equation, but again, trying to be cost effective as well. I would probably prioritize forced air heating as that covers the entire home and radiant floor would be for comfort rather than actual heating.
Still very much in the planning stages but really appreciate the assistance and any guidance or advice.

EDIT: I think I'm going to start a new thread so I don't hijack this one any further. I'll come back and add a link in case anyone would like to continue following along.
http://hvac-talk.com/vbb/showthread.php?t=1028551

The Synergy 3D is a great unit but keep in mind it can not heat the air at the same time as the water. While it does do water and space heating, its either or at any particular time. So as a backup it may not be the best application because if Radiant has priority over forced air it will just run all day long trying to satisfy the radiant load.
You could always do an NSW water to water unit and then do a NDZ split system with the gas furnace as a backup. The NDZ would be for domestic water and cooling and could run as a backup to radiant or do heating in the areas where they don't have radiant installed and worst case scenario you still have the backup gas furnace that can satisfy the whole houses heating load. This make sense?

Perryaire - I realize this thread is a little stale, but I'm wondering if you can give more details of the system you installed. I was just at a customers home this morning. The house is 7 years old with a 93% 2-stage bryant propane furnace and a 3.5 ton single stage AC currently serving their HVAC needs. When the house was built, the HO put radiant tube in the entire basement as well as the rooms on the upper floors with hard surface flooring. It's a total of 4 zones (5 if the garage is included - served by a hot water heater with radiant floor currently) of hydronic and the forced air is also zoned for the main and upper floors.

I'm thinking a water to water unit makes sense, but I'm trying to balance things out. The entire house isn't going to be able to be heated by radiant so I'll need to have a lot of space heating by the forced air unit and the higher temperatures required by a water coil on top of the furnace compared to the lower temps of the radiant floor adds a bit of a wrinkle to everything.

I have a perfectly serviceable furnace to use for backup, otherwise I very much like your use of a boiler as both auxiliary and DHW production. I'll offer that as an option, but I don't known that it's a necessary expense at this point for the HO. I'm looking into the Waterfurnace Synergy3D as a potential option - it seems like it might be a good fit, but that would be doing away with the furnace and then we're probably looking at electric as auxiliary backup, which really isn't a big deal I suppose as the current furnace doesn't have a VS blower either.

Any more details you can share would be appreciated. Thanks!

Benefits of Water:

The human body, which is made up of between 55 and 75 percent water,
Lack of water can lead to dehydration, a condition that occurs when you don't have enough water in your
body to carry on normal functions....

Yes, we used a w to w hp.
We are also using a boiler for the hot water heater as backup and summer hot water.
We have one air handler and a convector to do the small area in the basement.
We can easily add more convectors if they decide to expand the house.
I have decided that w to w is one of the best ways to really do a house.
I would do mine that way if I were starting from scratch.
We also di radiant floors in two sections of the house.

Chilled water

Did you use a reversible W to W unit and chilled water for cooling?

Water to Water Geothermal

We just did our first water to water Geo! It turned out awesome!
Customer loves it, we did two sections of the house with radiant floor heat, used a variable speed air handler for the cooling of the main section, added a convector in the basement for heating and cooling.
The old part of the house is radaitors, we have a Triangle tube solo 110 doing that and an indirect hot water heater for the domestic.
A lot of stuff going on for sure.