If you have a constantly leaking air conditioning system then yes it is worth swapping out. Especially if it runs off of the old r22.

13 seer is the federal minimum standard. It is relatively easy to get 16 seer without going with high-end equipment. Check with your local utility to see if they offer rebates for doing so. When people speak of a matched system, that means the combination of equipment has an ahri number registered to it listing it's capacity as well as efficiency. I believe you are in the epa's Southeast region so I think the ac equipment is already higher efficiency by default.

Sizing is important for AC systems. Oversizing equipment is almost always a bad idea. During periods of lower heat load the unit will cycle much more frequently. It takes about 10 minutes for the system to completely get up to full cooling capacity. And you can almost equate a an ac system cycling on and off more frequently versus running for longer periods like City mileage vs. Highway mileage for a car. Most brands are pretty good. Honestly the installation quality counts more then the brand.

I see you are in Arizona. I do not know what kind of heating source you have, if it's electric heat strips in an air handler, gas furnace or a heat pump. I am a large proponent of heat pumps as any way you can keep the electric heat strips off you will be saving yourself energy. If your ductwork is located in an unconditioned space like an attic or crawl space. Duct sealing is a prudent move if it is leaky. there is a furnace blower door test that can be done to see how much loss your ductwork has. If you have any other questions or proposals that have been given to you it would be interesting to discuss further.

Ronnie nailed it for the most part. The sizing,install, and the contractor that backs up the install is more important than the brand itself. Most folks wait until the unit goes kaput to replace it. You are in the drivers seat since there is not a gun to your head. "Their own brand, "Made in America" That is a rebranded Goodman (there is a STL dealer that sells them at a premium as "emerald" they are called). Most HVAC gear is made in Mexico. Lennox, Rheem/Ruud, York and Nordyne. Trane, Goodman and Carrier(although they are shipping production south in the near future [their coils are already made in Mexico]) are still made in the US. Goodman is a value brand and have their market niche but if you can afford it, go elsewhere. Replacing the line-set is eh. If you have a leak it is 97 times out of 100 the evaporator coil. The only two line-sets I've ever seen leak had a roofing nail go through it or a drywall screw. They are thick where as the evaporator coils are rifled thin for better heat transfer. Make sure you have an AHRI matched system to guarantee* performance. *Ratings do not include how good or bad the ductwork is. How cold does it get where you live? The model number of the furnaces means that they are 100K btu for a total of 200k btu for your house. That is a lot of heat. I don't know your region so I won't speak to sizing but the York bid seems quite reasonable. I would recommend getting one or two more bids for good measure.

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Looks like you did well. Keep those filters clean and try to use the fiberglass ones if you can.