What's a radio stack really cost?

I'm looking at a Skymaster that is mechanically in very good shape, but
is absolutely (just barely) VFR. It has more boat anchors in it than
Tracker Boats sells in a month. So..if a mid-time multi-rated,
instrument pilot was going to spend money on a new radio stack, how much
would he or she have to spend?



I'm assuming something along the lines of the following:



* GMA 340 audio panel

* GMX 200/traffic MFD

* Dual SL30 nav/comms

* GPS 400 gps

* GTX 330 transponder

* MD 200 VOR/LOC/GS indicator

* GI 102 VOR/LOC indicator

* GDL 69 XM receiver



I figure by breaking out the nav/comm function from the gps function, I
can lose either and still shoot an approach. I think my single point of
failure might be audio panel, but I don't know how to get around that
issue. The txponder is also an spof, but so what? Same with the XM
receiver.



I'd like to read feedback from folks that have been-there, done-that,
and have the tee-shirt. I'd also like to know how much I should expect
this stack to really cost (budgetary purposes).