Went through the same woe last year. Having just one FM immune COM, and a lack of panel space, and trying to improve the thing as well, the figure for me were:
GNS430: 5492
KR87: 2964
CAA Minor Mod: 64
14-28V converter: 160
New blind encoder: 150
2nd Used NSD360 HSI: 200
With the installation& VAT, this came out at about 13K - gulp!, but give me
FM Immune COM1/2 & NAV1, IFR GPS, HSI (non-slaved), and ADF that works (the old Bendix T12 had pretty much all but given up the ghost), and 2 ILS's (one of which isn't FM immune, but not required for a Private CofA)
Next to do is change the Nav112 for a later one to make it FM immune, but I'm letting the rush die down for them, as well as getting over the financial hit of the last lot
[ 23 September 2001: Message edited by: Awful Charlie ]