KX155 KX 155A Anybody know the difference?

The KX155 in my "new" airplane (Helio Courier) seems to have bitten the
dust. It looks like an old POS and I am trying to figure out what to do.
What are the functional differences between the KX155, KX165 and the KX155A
and KX165A? The airplane has a Garmin 300XL as #1 and a switching relay to
allow the 300XL or the KX155 to drive the HSI. I am trying to decide what
to do.

My options a

A:
#1 Garmin 430
#2 KX155
Get rid of the "GPS/NAV" switch/annunciator box

B:
Same as A but with 530. Pricey, but I could just buy the tray and
connectors and shuttle the 530 in my MU-2 back and forth until Garmin has
WAAS and then buy a 530A for the MU-2. This has the advantage of presumably
saving the cost of the WAAS upgrade thereby reducing the 530 premium
somewhat.

C:
#1 Currently installed 300XL.
#2 KX 155 or 165 I would prefer the 165 since I can get rid of the converter
box that drives the HSI.
Keep the GPS/NAV switch/annunciator box

The advantage of going with a 430 or 530 is that I have flown them for 800+
hrs and am comfortable with the operating logic. I can't say the same about
the 300X:L.

Cost is an issue. This is a second airplane and I anticipate using it 95%
VFR. I would rather spend the money on floats or skis :-). Since the
airplane may be left unattended in the backcountry for days at a time, I
would also like avionics that are not very attractive to a thief.

What do you think?

Mike
MU-2