I own a '78 C-172XP and I wish to upgrade my old Cessna/Collins avionics with new gear. I already bought an L-3 i-Link which is similar to GarminAT's MX20.

I am looking at a Garmin 347 or a PS Engineering PM8000 for the audio upgrade on one hand and either a Garmin 430 or a GarminAT 480. Can any body give suggestions on my picks.

I am not sure which of the audio panels is better (I do like the idea of having auto-squelch and a connection for a cellular phone). In addition, I know little about GPS technology. One thing I see is that Garmin's [sales] number favors the 430 but Garmin wants to "extract" an additional $2000 from me in the Fall to bring the unit to WAAS level and provide IFR approach certification. On the other hand, the 480 is already WAAS and IFR approach certified but it has no moving map and it is reported to be less user-friendly. Would a Bendix King KLN GPS do as well?

Lastly, I measured 12.5 inches vertically in the center portion of my C-172 center panel but I would like to know if I can squeeze more stuff in. Any body knows what is the maximum height available to locate NavComs in the center portion of a C172 panel?