There is an interesting variety of ways to control the waste gate on turbocharged airplanes. And of course a wide range of engineering quality for the whole installation. For the purposes of this discussion I would break them down into three levels.
The minimum engineering modification with stock 8 to 8.7 to compression ratio pistons and simple wastegate (often manually controlled). These can retain pretty good performance (the higher induction temp means you need to boost manifold pressure by a few inches to maintain HP). They only weigh 25-50lbs per engine. And theoretically these simple wastegate controllers are easier to maintain and troubleshoot. The downside is that the installation is often under engineered, resulting in heat or vibration or cracking problems under the cowling. They are also more demanding of the pilot. There is a lot more potential for overboost, and with the stock pistons, there is less detonation margin. If timing is off, or the ignition system is not maintained, or injector plugged, or plenty of fuel is not provided these installations are much more susceptible to accelerated wearing out of or plain wrecking of cylinders. With a reduced detonation margin, the "redbox" of potential detonation is much larger.
Next, the still under engineered factory planes (and some of the better stc'd ones) that were widely marketed in the late 60s and 70s. These airplanes still had simple wastegate controllers but compression ratio reduced to maintain detonation margin and manifold boosted up around 36-41" to maintain power. They were more tolerant of sub-optimal maintenance or pilot technique but performance and efficiency sucked. Kind of like the recalled vw diesels with compression ratio dialed down. Over the years I worked for operators that had in the fleet both turbo and NA versions of the same plane. Bonanza, Arrow, and 310/340. I was a young consumer of aviation marketing magazines in the 70s when manufacturers were racing to come out with turbo versions of everything in their lineup. They planes were pimped as a big jump in performance with impressive speed and altitude potential. I was pretty stumped when I actually flew them. In every case the NA plane easily outperformed the turbo at any altitude that didn't require oxygen. Full throttle and S/E performance was better up to 5,000', and cruise performance was better up to 10,000'. Whenever you did a two ship mission, the turbo would take off first and land second and burn 20% more fuel. Generally though you didn't have to fuss with the mixture for takeoff and climb, so the workload could be lower.
Eventually the quality was brought up to the fully engineered systems like the ones on a 404/421, Chieftan, Columbia 400 and others that I am not as familiar with. These still had the lower compression pistons, so fuel efficiency was reduced, but they got sophisticated waste gate controllers, tuned induction, intercoolers and they were boosted up to provide horsepower above what any NA plane could produce. Often a bitch to work on though and 25-40% more expensive to run per mile than the NA version.
But this all pretty academic right? Is there anywhere to buy a turbo kit for a 500? It seems like turbo'd airplanes do come up for sale. What level of quality is the turbo installation? The better ones, like Chieftan level should up the performance but at a significant weight and cost and fuel burn penalty.
As long we are fantasizing, the fadec Lycoming that Cape Air is running in their Tecnam 2012s would be an awesome Shrike engine if they ever get it sorted out.
In a less fantastic world I would rather have the plane that Ted designed for this mission 60 years ago than an aftermarket turbo install. IGSO 540s seem to be considered unmaintainable in the Commander community, but I saw a lot of T-bones and several Queen Airs at OSH, and some of them had the big supercharged motors.
But all of those options are well beyond my means. I can only afford the approach that JimC describes - keep the weight down and be realistic about your options.
Maybe eventually I will be able to afford some new blueprinted engines. I believe ported and polished and flow matched E1B5's will produce 300hp on the dyno. Supposedly there are engine builders who, if you ask tactfully, will install 9.0-1 or even 9.5 pistons while they have your new cylinders off for rework. You would be giving up some of your detonation margins, same as the first turbo example described, but fuel efficiency is improved if you can safely operate lean. Finally, if you had a good relationship with a shop (or you were your own shop) you could swap governers for ones that would let you turn 2700 rpms. Then you would have a plane with expensive (to buy, not to run) 325ish hp engines with no weight penalty or complexity, that would outperform a turbo shrike on one engine up to 7500' and out cruise it up to 12,000'.