In the US or in Europe?
If in Europe, then I can wohleheartedly recommend the TT31 transponder. In connection with a 430W it will do ADSB out quite nicely indeed (physically it also will with a normal 430 but it is not really allowed to). It is a relatively low price item (and you can still sell your Mode C stuff in the US) but worth doing away with the hasssle of figuring out which airspace you can fly in without it.
A 430 is probably still a lot more value than a KLN94 simply also because it includes the 8.33 you will need. Clearly, you can get KLN’s for a big bargain but it is old technology whereas the 430 is as well but not that old and with a lot more utility.
As you own the ADF, if it works, why not leave it in. If it’s a KR87, it has a nice stopwatch feature which was the reason I kept mine.
Autopilot: If you are thinking the low STEC models, I’d go for the system 30 instead of 20. Altitude hold is worth the difference on any day. It won’t hold a glideslope though, for that you either need a 60-2 or a 55×. S-Tec used to give massive discounts on the 55X when you were interested in buying a 30, that is how I got mine. Friedrichshafen is a good place to hunt for that kind of discount.
If you have a 430 and an S-Tec, GPSS is an issue. S-TEC have a converter or you can go for one of the cheaper Aspens (like the E5) which has GPSS inbuilt. Obviously a E5 gives a lot more for not that much more money than a simple converter.
My 2 cents worth. Frankly said, it takes a lot of discipline not to overequip while you are at it, but it does help to think it through what you want or not. In my own experience, I could probably do without a lot of stuff but I like the AP for travelling.
M_D it is in the UK. The ADF is old skool with dial tuning so quite retro.
Is there any value to the old King 170 Nav/Com? I probably will keep one CDI display, but is there experience of selling old NAV/COMs in the USA?
A search on US Ebay is worth doing.
Some stuff sells well, other stuff doesn’t. I sold my KCS55 slaved compass system parts very quickly; people keep theirs going off Ebay it seems, very cost-effectively. But it has to be said that is a good system which does what it says on the box and it’s been doing it for 40 years.
I would expect a 170 to be worthless.
…it sports a Bendix T12D ADF, nice door stop for the garden shed.
Are King KX-155 NAV/COM more valuable? I have an old one which is unserviceable in the UK as no longer able to be fitted post .833.
Presumably of some value to a US buyer, but would they bid on a UK sourced, as is piece of kit?
This search shows that a KX155 can fetch a quite reasonable price, especially if it “looks good” e.g. you get an 8130-3 generated (N-reg owners don’t need one, contrary to popular belief, but it helps to sell something because many people don’t know this).
US buyers are indeed suspicious of European sellers. I have sold a lot of stuff on US Ebay so have seen this. One guy told me, back in the Gulf War days when a certain European country refused to participate in some allied action and drew criticism from the US govt, a large number of US buyers received bricks (from sellers in that country) instead of avionics. You need to produce a really nicely written detailed listing, with good quality photos, and generally looking like you have gone to school at some stage and are a reasonably diligent person – IOW, you need to do better than the average Ebay seller That strategy attracts the better quality buyers (same in all walks of life really).
The shipping cost (DHL or similar) isn’t going to be cheap – of the order of £150. Below 2kg it can go registered airmail but IIRC you can’t get compensation for more than £250 and it can take 5-10 days. That option is about £20. With decent packaging, 2kg is hard to achieve.
If you use Advanced Search and check fhe Completed Listings box, you see what the items actually sold for.
US Ebay is great. The stuff is almost worthless in Europe, because most people cannot (or are afraid to) self install, and because for EASA-regs all used stuff needs an EASA-1 form, and even most N-reg owners don’t know their options.