Heat Pumps and Electric Heating - advice on new HVAC system (Oil+Heat pump)

Hi, I have few questions about a system I am thinking about installing in my home that I was hoping someone could give me some advice on.

First some background. I live near Columbus OH and I bought this house 3.5 years ago and it's 2200 sqft. The current central air, heating and cooling system is about 15 years old and it is an oil furnace. The first year I was in the house we replaced the heat exchanger due to a crack. Now we are being told that the heat exchanger is cracked again. The heat exchanger is covered but the install cost is around $700-800. You might ask what is wrong that would cause this much problem with the heat exchanger? Our guess is that when we move into the house we removed some center walls on the main floor and in doing this we took out a lot of cold air return volume. This in turn causes some excessive heat in the heat exchanger that causes increased stress?

Since I have been in the house I have been constatly putting money into this system so I am thinking about starting over. In addition with the rising cost of fuel and the above metioned maintenance I think that a new system could pay for itself in 5 to 10 years and we plan on being in this house for a long time.

We have a friend of the family that is an installer that is going to give us a pretty good deal, I think, but I am not sure if the brand name is exactly what I should be getting. Maybe someone can let me know if they there are any big concerns with this equipement

This is his proposal:

Comfort Air oil furnance OLRA125-D5
Goodman heat pump GSH14 (4 Ton 14 SEER)
AprilAir 600 humidifier and just a simple filter system (He said he doesn't think it's worth the money to buy an expensive filter)
In addition he is going to run a new cold air return to the 2nd floor and one additional to the main floor that will be sufficient for return air.
All this installed for $6,690.45

Any thought on if this is a good system or not. Sounds like Trane or Lennox system is the most popular on this forum. I thought about changing over to Propane backup but I would have to put in a tank and that is going to run between 1500-2000 so it is easy to stay with oil.
Is it worth going up to at least 15 SEER to get the $200 tax credit?

Any feedback is greatly appriciated.

Thanks

First go to http://warmair.net and compare fuel cost for there.
10 years yes go for a 15 seer on the AC . you need that to get the tax credit of $300 also go for the V/S blower tax credit of $50 on it. A pleated filter of not over a MERV 5 new every 30 to 90 days
AprilAir 600 humidifier good bet get it for sure.

Goodman heat pump GSH14 (4 Ton 14 SEER
No way get another brand Lennox, Trane, Rheem

ED ;)

Do you think that I can get away with electric backup or do you recomend oil or gas for back up. The installer I am working with recomends that I keep the oil for the really cold days.

Thanks for the help

Compare the fuel cost there for electric over the oil and see what you should do. All we put in or use here in Missouri is electric backup.

ED ;)