But if I do that I will need to relocate the audio panel, the transponder and the autopilot (in the center console, between the seats, below the engine levers) to the far right of the panel. I am sure it is possible (I have seen a Columbia with that setup), but since I already have a MFD, although not for data entry, I am not sure it is worth my while. And then I would also need to reach all the way to the right for the XPDR and audio panel.
obviously a large screen GTN750 or even a 530 is not recommended when you have a full size PFD and MFD like the Avidyne installed in the Lancair Columbia
Also, in Europe, any large avionics job is Russian roulette; more so in a plane you have just bought and whose history is to some extent unknown. Actually it is much more risky than Russian roulette because a revolver has 6 positions, whereas the % of useless avionics shops is way higher than 16%, and anyway with RR your chances are slightly better than 5/6 because the extra weight causes a statistical bias on where the cylinder stops 
As you have a big MFD already, just get a very good “FMS box” and there are several options. FP transfer from a tablet is a nice feature, though obviously it doesn’t make the plane go any faster and I have no trouble getting around with my KLN94
Autopilot roll steering is something else to consider… again not a big thing but with a modern GPS the ability to e.g. fly holds hands-off is nice. I turned up at LFAT on Sunday and with four airborne planes waiting for the ILS (training flights I guess) I got the hold, as usual when there is more than 1 plane within 50nm of the IAP So I cancelled IFR and landed… but you can get these holds assigned with virtually no notice because the handover to the approach controller can be very late.
Aviathor wrote:
So if I understand correctly you are saying that the age of GTN430s (WAAS/non-WAAS) make them more prone to having problems, and for that reason I may be better off with a new set of radios?
Yes, that as what I am seeing for just over a year. The number of GNS units which fail, is higher then it used to be. This is also expected with age offcourse, though it seem to be quite an increase. This is something you need to take into account. Garmin offers fixed fee repairs for these, ranging in the 800 USD to 1500 USD ex VAT depending on the exact type.
Aviathor wrote:
It is also my understanding that the GNS430W is still being sold by Garmin, so I expect they will be supported for a while longer…
Currently only the support of the first generation GNS is ended (28 Volt only models). Other non WAAS GNS and WAAS GNS are still supported with this fixed repair fee. Garmin doesn’t sell the GNS anymore. What they do, is enable you to have a non waas GNS upgraded to a WAAS GNS. Garmin then modifies the excisting GNS to become a WAAS GNS.
Sir_Percy wrote:
The 430 is out of support which means that in case of a repair you might have to update it to a WAAS unit.
This is not correct. They can upgrade a GNS to a WAAS GNS if you want. When you have an older unit, which has failed, it might not be possible to upgrade it at all. If your GNS is still supported, they will not force you into a WAAS upgrade.
Sir_Percy wrote:
I think I read about the capability to crossfill between the 650 and 430 but it might only have been the 430W….
From my experiance, the crossfill will not always work, even when Garmin says so. If it works fine, it’s ok. I wouldn’t trust on that one though. Had a dual WAAS GNS installation the other day, where one unit was repaired by Garmin, afterwards the crossfill didn’t work anymore, even though the difference in software level shouldn’t be an issue, and both running same database. Yet a software update on the non repaired unit was needed to get it going again.
You can get rid both of audio panel (use remote controlled GMA35) and XPDR as both can be remote controlled from GTN and yes, it has a tremendous value to have a unit where you can do easy data entry. TREMENDOUS as it is the main advantage of the device. Actually, it is something you mentioned in the first post – loading airways and inputing flight plans. On GTN750 this is real easy, easier than on GARMIN 1000. Aspen, Avidyne or other MFD is merely your window, your display but not the main data entry device. GTN650 compared to GTN750 is pain in the ass.
However, a remotely controlled intercom like the GMA35 gives you a nasty single point of failure for all comms and all non-GPS nav: the GTN touch screen! With a bit of bad luck you may not be able to fly an ILS if the GPS screen fails. I would want to always be able to fly an ILS even if all GPS kit has failed i.e. just using a COM/NAV radio (or perhaps a standalone COM/NAV/GPS box like a GNS430 etc) and a real physical CDI.
Peter wrote:
However, a remotely controlled intercom like the GMA35 gives you a nasty single point of failure for all comms and all non-GPS nav: the GTN touch screen! With a bit of bad luck you may not be able to fly an ILS if the GPS screen fails. I would want to always be able to fly an ILS even if all GPS kit has failed i.e. just using a COM/NAV radio (or perhaps a standalone COM/NAV/GPS box like a GNS430 etc) and a real physical CDI.
This has a fail safe feature, if you have a GTN-750 with remote audio panel function, it will select other radio when switched off. So your second radio is always fully available.
For the single NAV / GPS display this risk is equal for all boxes.
