I am looking to purchase a King Air twin engine turboprop aircraft, and am looking at all options, whether new or an older model that can be upgraded with the Blackhawk XP135A engine package and the latest Garmin or Fusion avionics. It should be a pressurized cabin, able to carry six adults plus pilots, and all baggage (estimated 2000 pounds) at least 1000 miles. It should be able to land on relatively small airports, or unimproved fields Of all Beechcraft King Air models built since 1975, where upgrades of engines and avionics are available, what is the most economical model to fulfill this task?

To find the most economical Beechcraft King Air model that meets your criteria, several factors must be considered, including initial purchase cost, upgrade potential (engine and avionics), operating costs, and resale value. Here's a detailed analysis of suitable King Air models since 1975:

Criteria Recap:
Cabin Requirements: Pressurized cabin, able to carry six adults plus pilots.
Baggage Capacity: At least 2000 pounds of baggage.
Range: At least 1000 miles.
Landing Capabilities: Ability to land on small airports or unimproved fields.
Upgradability: Availability of Blackhawk XP135A engine package and modern avionics like Garmin or Pro Line Fusion.
Potential Models:
1. King Air 90 Series (C90, C90A, C90B, E90, F90)
Base Cost: $300,000 - $1 million, depending on age and condition.
Upgrade Potential: Can be equipped with Blackhawk XP135A engines and advanced Garmin avionics.
Cabin: Smaller than other King Airs, generally accommodates fewer passengers with less space.
Performance: Adequate for shorter runways and unimproved fields. The Blackhawk upgrade significantly improves speed and range, but the cabin size might limit comfort for eight passengers and ample baggage.
Economics: Generally, the most economical for initial purchase and upgrades.
2. King Air 100 Series
Base Cost: $500,000 - $1.5 million.
Upgrade Potential: Can be upgraded but lacks the same extensive support for Blackhawk engine upgrades as the 90 and 200 series.
Cabin: Larger than the 90 series, suitable for more passengers and baggage.
Performance: Decent range and ability to handle unimproved strips, but availability of parts and upgrades may be more limited.
3. King Air 200/B200 Series
Base Cost: $800,000 - $3 million.
Upgrade Potential: Widely available Blackhawk XP135A engine upgrades and advanced avionics options like Garmin G1000 NXi or Pro Line Fusion. Can also be fitted with saddle tanks for extended range.
Cabin: Comfortable for six adults plus pilots, with a pressurized cabin.
Performance: Excellent range and payload capacity, capable of meeting the 2000 pounds of baggage and 1000-mile range requirement. Good for small airports and unimproved fields with suitable landing gear and propeller options.
Economics: Higher initial cost but excellent upgradability and resale value. A well-rounded choice for performance and comfort.
4. King Air 300/350 Series
Base Cost: $1.5 million - $6 million.
Upgrade Potential: Advanced avionics and engine upgrades available. Blackhawk upgrades are less common since these models already come with more powerful engines.
Cabin: Largest cabin among the options, with ample space for passengers and baggage.
Performance: Superior performance, longer range, and excellent STOL (short takeoff and landing) capabilities. Best for comfort and capabilities but comes with higher operating and acquisition costs.
Recommendation:
The King Air B200 series stands out as the most economical choice that meets all your criteria:

Initial Purchase: More affordable compared to the 300/350 series.
Upgrade Potential: Extensive options for engine and avionics upgrades, enhancing performance and safety.
Cabin and Comfort: Adequate size for six passengers plus pilots and significant baggage capacity.
Performance: Excellent range, payload, and ability to operate from unimproved fields.
By opting for a B200 model from the 1980s or 1990s, you can invest in upgrades to achieve modern performance and comfort standards, making it a cost-effective and versatile aircraft for private use. The resale value of the B200 series, especially with upgrades, remains strong, further enhancing its appeal.

Adam, how many hours in the Aerostar did you have before embarking on the Instrument rating in it?

Everyone here is gong to rip you for having those ambitious goals, but I actually don't see any problems with them if you're willing to put in the time and work. ...

Be prepared to be a full time student, total immersion, no half buttedness. I'd say getting your PPL and instrument in a basic trainer, and then the multi commercial instrument in something with all the bells and whistles is appropriate.